US 6,027,887 AGrant
MN Gene and Protein
Issue Date:2000-02-22
•10 Claims
•14 Drawing Sheets
Abstract
Herein disclosed is a novel oncogene named MN or alternatively MN/CA IX. The MN protein has been determined to be the first tumor-associated carbonic anhydrase isoenzyme that has been described. Abnormal expression of the MN gene is shown to signify oncogenesis, and diagnostic/prognostic methods for pre-neoplastic/neoplastic disease to detect or detect and quantitate such abnormal MN gene expression, e.g., immunoassays and nucleic acid hybridization assays, are provided. Also disclosed are methods to treat pre-neoplastic/neoplastic disease involving the MN gene and protein, e.g., methods comprising the use of MN-specific antibodies, conjugated or unconjugated to cytotoxic agents, and the use of MN antisense nucleic acids.
Metadata
Assignee
- Institute of Virology, Solvak Academy of Sciences
Inventors
- Jan Zavada
- Silvia Pastorekova
- Jaromir Pastorek
Application Information
Application Number:US 7877390
Filing Date:1997-01-24
Priority Date:1992-10-21
Art Unit:164
Classifications
IPC:
C12Q 168C07H 2102C07H 2104
Field of Search:
435536935623.1;24.376;77;78
Patent Drawings (14 sheets)
Description
FIELD OF THE INVENTION
The present invention is in the general area of medical genetics and in the fields of biochemical engineering, immunochemistry and oncology. More specifically, it relates to the MN gene--a cellular gene considered to be an oncogene, which encodes the oncoprotein now known alternatively as the MN protein or the MN/CA IX isoenzyme.
BACKGROUND OF THE INVENTION
Zavada et al., International Publication Number WO 93/18152 (published Sep. 16, 1993) and U.S. Pat. No. 5,387,676 (issued Feb. 7, 1996), describes the elucidation of the biological and molecular nature of MaTu which resulted in the discovery of the MN gene and protein. The MN gene was found to be present in the chromosomal DNA of all vertebrates tested, and its expression to be strongly correlated with tumorigenicity.
The MN protein is now considered to be the first tumor-associated carbonic anhydrase (CA) isoenzyme that has been described. Carbonic anhydrases (CAs) form a large family of genes encoding zinc metalloenzymes of great physiological importance. As catalysts of reversible hydration of carbon dioxide, these enzymes participate in a variety of biological processes, including respiration, calcification, acid-base balance, bone resorption, formation of aqueous humor, cerebrospinal fluid, saliva and gastric acid [reviewed in Dodgson et al., The Carbonic Anhydrases, Plenum Press, New York-London, pp. 398 (1991)]. CAs are widely distributed in different living organisms.
In mammals, at least seven isoenzymes (CA I-VII) and a few CA-related proteins (CARP/CA VIII, RPTP-.beta., RPTP-.tau.) had been identified [Hewett-Emmett and Tashian, "Functional diversity, conservation and convergence in the evolution of the alpha, beta and gamma carbonic anhydrase gene families," Mol. Phyl. Evol., 5: in press (1996)], when analysis of the MN deduced amino acid sequence revealed a striking homology between the central part of the MN protein and carbonic anhydrases, with the conserved zinc-binding site as well as the enzyme's active center. Then MN protein was found to bind zinc and to have CA activity. Based on that data, the MN protein is now considered to be the ninth carbonic anhydrase isoenzyme--MN/CA IX. [Opavsky et al., Genomics, 33: 480-487 (May 1996)]. [See also, Hewett-Emett, supra, wherein CA IX is suggested as a nomenclatural designation.]
CAs and CA-related proteins show extensive diversity in both their tissue distribution and in their putative or established biological functions [Tashian, R. E., Adv. in Genetics, 30: 321-356 (1992)]. Some of the CAs are expressed in almost all tissues (CA II), while the expression of others appears to be more restricted (CA VI and CA VII in salivary glands). In cells, they may reside in the cytoplasm (CA I, CA II, CA III, and CA VII), in mitochondria (CA V), in secretory granules (CA VI), or they may associate with membrane (CA IV). Occasionally, nuclear localization of some isoenzymes has been noted [Parkkila et al., Gut, 35: 646-650 (1994); Parkkilla et al., Histochem. J., 27: 133-138 (1995); Mori et al., Gastroenterol., 105: 820-826 (1993)].
The CAs and CA-related proteins also differ in kinetic properties and susceptibility to inhibitors [Sly and Hu, Annu. Rev. Biochem., 64: 375-401 (1995)]. In the alimentary tract, carbonic anhydrase activity is involved in many important functions, such as saliva secretion, production of gastric acid, pancreatic juice and bile, intestinal water and ion transport, fatty acid uptake and biogenesis in the liver. At least seven CA isoenzymes have been demonstrated in different regions of the alimentary tract. However, biochemical, histochemical and immunocytochemical studies have revealed a considerable heterogeneity in their levels and distribution [Swensen, E. R., "Distribution and functions of carbonic anhydrase in the gastrointestinal tract," In: The Carbonic Anhydrases. Cellular Physiology and Molecular Genetics, (Dodgson et al. eds.) Plenum Press, New York, pages 265-287 (1991); and Parkkila and Parkkila, Scan J. Gastroenterol., 31: 305-317 (1996)]. While CA II is found along the entire alimentary canal, CA IV is linked to the lower gastrointestinal tract, CA I, III and V are present in only a few tissues, and the expression of CA VI and VII is restricted to salivary glands [Parkkila et al., Gut, 35: 646-650 (1994); Fleming et al., J. Clin. Invest., 96: 2907-2913 (1995); Parkkila et al., "Membrane-bound carbonic anhydrase IV is expressed in the luminal plasma membrane of the human gallbladder epithelium," Hepatology, in press].
MN/CA IX has a number of properties that distinguish it from other known CA isoenzymes and suggest its relevance to oncogenesis. Those properties include its density dependent expression in cell culture, (e.g., HeLa cells), its correlation with the tumorigenic phenotype of somatic cell hybrids between HeLa and normal human fibroblasts, its close association with several human carcinomas and its absence from corresponding normal tissues [Zavada et al., Int. J. Cancer, 54: 268-274 (1933); Pastorekova et al., Virology, 187: 620-626 (1992); Liao et al., Am. J. Pathol., 145: 598-609 (1994); Pastorek et al., Oncogene, 9: 2788-2888 (1994)]. In addition, the in vitro transformation potential of MN/CA IX cDNA has been demonstrated in NIH 3T3 fibroblasts [Pastorek et al., id.].
The MN protein was first identified in HeLa cells, derived from a human carcinoma of cervix uteri. As indicated above, MN gene expression is strongly associated with tumorigenicity. It is found in many types of human carcinomas (notably cervical, ovarian, endometrial, renal, bladder, breast, prostate among others). Very few normal tissues have been found to be express MN protein to any significant degree. As detailed herein, those MN-expressing normal tissues include the human gastric mucosa and gallbladder epithelium, and some other normal tissues of the alimentary tract. Paradoxically, as shown herein, MN gene expression has been found to be lost or reduced in carcinomas and other preneoplastic/neoplastic diseases related to the gastric mucosa, gallbladder epithelia and those other tissues of the alimentary tract. Thus, in general, it appears as elucidated by Examples 1 and 4-7 below, that oncogenesis may be signified: (1) when MN protein is present in a tissue which normally does not express MN protein to any significant degree; (2) when MN protein is absent from a tissue that normally expresses it; or (3) when MN gene expression is at a significantly reduced level from that normally expressed in a tissue.
SUMMARY OF THE INVENTION
The discovery of the MN gene and protein and thus, of substantially complementary MN genes and proteins encoded thereby, led to the finding that the expression of MN proteins was associated with tumorigenicity. That finding resulted in the creation of methods that are diagnostic/prognostic for cancer and precancerous conditions. Methods and compositions are provided for identifying the onset and presence of neoplastic disease by detecting or detecting and quantitating abnormal MN gene expression in vertebrates.
Such abnormal MN gene expression can be detected or detected and quantitated by a variety of conventional assays, for example, by immunoassays using MN-specific antibodies to detect or detect and quantitate MN antigen, or by hybridization assays using MN nucleic acids, such as, MN cDNA, to detect MN mRNA in a vertebrate sample. Such vertebrate samples, preferably mammalian, more preferably human, can include tissue sections, tissue extracts, tissue smears, cells (whole or lysed), and cell extracts. MN antigen, preferably in a soluble form, more preferably as the MN extracellular domain, can also be found in body fluids as an indicator of preneoplastic/neoplastic disease.
Preferred body fluids to assay according to this invention include blood, serum, plasma, semen, breast exudate, saliva, tears, sputum, mucous, urine, gastric secretions, fecal suspensions, bile, lymph, cytosols, ascites, pleural effusions, amniotic fluid, bladder washes, bronchioalveolar lavages and cerebrospinal fluid.
Preferred samples and body fluids would in general depend upon the type of preneoplastic/neoplastic disease for which the diagnosis/prognosis is sought. For example, serum could be a more preferred body fluid to test for renal cell carcinoma, breast, bladder or prostate cancer; however, urine could be a more preferred body fluid to test for urinary tract tumors, as renal cell carcinoma or bladder cancer. Still further preferred for testing for abnormal MN gene expression associated with urinary tract cancer, especially bladder cancer, could be exfoliated cells from urine. Mucous from the intestines and fecal suspensions could be preferred samples to test for duodenal, ileal, jejunal, and/or colorectal cancers, whereas gastric secretions and bile could be preferred body fluids to test respectively for stomach, and gallbladder/liver duct cancers.
The present invention is useful for detecting a wide variety of neoplastic and/or preneoplastic diseases. Exemplary diseases include carcinomas, such as mammary, prostate, bladder, renal, ovarian, gastrointestinal, uterine, cervical, endometrial, squamous cell and adenosquamous carcinomas; and head and neck cancers; mesodermal tumors, such as neuroblastomas and retinoblastomas; sarcomas, such as osteosarcomas and Ewing's sarcoma; and melanomas. Of particular interest are head and neck cancers, gynecologic cancers including ovarian, cervical, vaginal, endometrial and vulval cancers; gastrointestinal cancer, such as, stomach, colon, rectal, intestinal and esophageal cancers; urinary tract cancer, such as, bladder and kidney cancers; skin cancer; liver cancer; prostate cancer; lung cancer; and breast cancer. Of still further particular interest are gynecologic cancers; breast cancer; urinary tract cancers, especially bladder cancer; lung cancer; and liver cancer. Even further of particular interest are gynecologic cancers and breast cancer. Gynecologic cancers of particular interest are carcinomas of the uterine cervix, endometrium and ovaries; more particularly such gynecologic cancers include cervical squamous cell carcinomas, adenosquamous carcinomas, adenocarcinomas as well as gynecologic precancerous conditions, such as metaplastic cervical tissues and condylomas.
As indicated above, most normal tissues do not express MN protein. Thus, for most preneoplastic/neoplastic diseases, abnormal MN gene expression is indicated by the presence, e.g., of MN protein and/or MN mRNA in a vertebrate sample, a higher level of MN gene expression being associated with a poorer prognosis. However, as demonstrated herein, the reverse is true for preneoplastic/neoplastic disease associated with the gastric mucosa, gallbladder epithelium, and certain other tissues of the alimentary tract including small intestinal (duodenal, jejunal and ileal), colorectal, pancreatic duct and liver duct tissues. MN protein is normally expressed abundantly in the gastric mucosa and gallbladder epithelium and is normally also expressed, but to lesser extent, in those other tissues of the alimentary tract. However, in the case of preneoplastic/neoplastic disease, MN protein is absent from or at a reduced level of expression in the gastric mucosa, gallbladder epithelium and in those other alimentary tract tissues. The absence or reduced expression in those gastrointestinal and other alimentary tract tissues is thus indicative of oncogenesis, and signaled, for example, by the absence or reduced amount of MN protein and/or MN gene transcription in vertebrate samples.
The immunoassays of this invention can be embodied in test kits which comprise MN proteins/polypeptides and/or MN-specific antibodies. Such test kits can be in solid phase formats, but are not limited thereto, and can also be in liquid phase format, and can be based on immunohistochemical assays, ELISAS, particle assays, radiometric or fluorometric assays either unamplified or amplified, using, for example, avidin/biotin technology.
Test kits of this invention can comprise the nucleic acid probes of the invention which are useful diagnostically/prognostically for neoplastic and/or preneoplastic disease. Preferred test kits comprise means for detecting or measuring the hybridization of said probes to the MN gene or to the mRNA product of the MN gene, such as a visualizing means.
Further, this invention is directed to the MN gene, fragments thereof and the related cDNA which are useful, for example, as follows: 1) to produce MN proteins/polypeptides by biochemical engineering; 2) to prepare nucleic acid probes to test for the presence of the MN gene in cells of a subject; 3) to prepare appropriate polymerase chain reaction (PCR) primers for use, for example, in PCR-based assays or to produce nucleic acid probes; 4) to identify MN proteins and polypeptides as well as homologs or near homologs thereto; 5) to identify various mRNAs transcribed from MN genes in various tissues and cell lines, preferably human; and 6) to identify mutations in MN genes. The invention further concerns purified and isolated DNA molecules comprising the MN gene or fragments thereof, or the related cDNA or fragments thereof.
Thus, this invention in one aspect concerns isolated nucleic acid sequences that encode MN proteins or polypeptides wherein the nucleotide sequences for said nucleic acids are selected from the group consisting of:
(a) SEQ. ID. NO.: 1;
(b) nucleotide sequences that hybridize under stringent conditions to SEQ. ID. NO.: 1 or to its complement;
(c) nucleotide sequences that differ from SEQ. ID. NO.: 1 or from the nucleotide sequences of (b) in codon sequence because of the degeneracy of the genetic code. Further, such nucleic acid sequences are selected from nucleotide sequences that but for the degeneracy of the genetic code would hybridize to SEQ. ID. NO.: 1 or to its complement under stringent hybridization conditions.
This invention also concerns MN genomic sequences shown in FIGS. 2A-F, that is, SEQ. ID. NO.: 5, as well as sequences that hybridize to it or its complement under stringent conditions, or would hybridize to SEQ. ID. NO.: 5 or to its complement under such conditions, but for the degeneracy of the genetic code. Degenerate variants of SEQ. ID. NOS.: 1 and 5 are within the scope of the invention.
Further, this invention concerns nucleic acid probes which are fragments of the isolated nucleic acids that encode MN proteins or polypeptides and/or are from the MN genomic sequence. Preferably said nucleic acid probes are comprised of at least 29 nucleotides, more preferably of at least 50 nucleotides, still more preferably at least 100 nucleotides, and even more preferably at least 150 nucleotides.
Still further, this invention is directed to isolated nucleic acids containing at least twenty-five nucleotides selected from the group consisting of:
(a) SEQ. ID. NOS.: 1, 3, 5, 7-9, 17, 18, 27-49, 55-66 and 88-96, and sequences that are complementary to SEQ. ID. NOS.: 1, 3, 5, 7-9, 17, 18, 27-49, 55-66 and 88-96;
(b) nucleotide sequences that hybridize under standard stringent hybridization conditions to one or more of the following nucleotide sequences: SEQ. ID. NOS.: 1, 3, 5, 7-9, 17, 18, 27-49, 55-66 and 88-96, and the respective complements of SEQ. ID. NOS.: 1, 3, 5, 7-9, 17, 18, 27-49, 55-66 and 88-96; and
(c) nucleotide sequences that differ from the nucleotide sequences of (a) and (b) in codon sequence because of the degeneracy of the genetic code. The invention also concerns nucleic acids that but for the degeneracy of the genetic code would hybridize to the nucleic acids of (a) and (b) under standard stringent hybridization conditions. Further this invention concerns nucleic acids of (b) and (c) that hybridize partially or wholly to the non-coding regions of SEQ. ID. NO.: 5 or its complement as, for example, sequences that function as nucleic acid probes to identify MN nucleic acid sequences. Conventional technology can be used to determine whether the nucleic acids of (b) and (c) or of fragments of SEQ. ID. NO.: 5 are useful to identify MN nucleic acid sequences, for example, as outlined in Benton and Davis, Science, 196: 180 (1977) and Fuscoe et al. Genomics, 5: 100 (1989). In general, such nucleic acids are preferably at least 29 nucleotides, most preferably at least 50 nucleotides and still more preferably at least 100 nucleotides. An exemplary and preferred nucleic acid probe is SEQ. ID. NO.: 55 (a 470 bp probe useful in RNase portection assays).
Fragments of the isolated nucleic acids of the invention, can also be used as PCR primers to amplify segments of MN genes, and may be useful in identifying mutations in MN genes. Typically, said PCR primers are olignucleotides, preferably at least 16 nucleotides, but they may be considerably longer. Exemplary primers may be from about 16 nucleotides to about 50 nucleotides, preferably from about 19 nucleotides to about 45 nucleotides.
Further, the invention concerns the use of such PCR primers in methods to detect mutations in an isolated MN gene and/or fragment(s) thereof. For example, such methods can comprise amplifying one or more fragment(s) of an MN gene by PCR, and determining whether any of said one or more fragments contain mutations, by, for example, comparing the size of the amplified fragments to those of similarly amplified corresponding fragments of MN genes known to be normal, by using a PCR-single-strand conformation polymorphism assay or a denaturing gradient gel electrophoretic assay.
This invention also concerns nucleic acids which encode MN proteins or polypeptides that are specifically bound by monoclonal antibodies designated M75 that are produced by the hybridoma VU-M75 deposited at the American Type Culture Collection (ATCC) at 12301 Parklawn Drive in Rockville, Md. 20852 (USA) under ATCC No. HB 11128, and/or by monoclonal antibodies designated MN12 produced by the hybridoma MN 12.2.2 deposited at the ATCC under ATCC No. HB 11647.
This invention further concerns isolated nucleic acids containing at least sixteen nucleotides, preferably at least twenty-nine nucleotides, more preferably at least fifty nucleotides, wherein said nucleic acid is selected from the group consisting of:
(a) the MN nucleic acids contained in plasmids A4a, XE1 and XE3 which were deposited at the American Type Culture Collection (ATCC) in Rockville, Md. in the United States of America under the respective ATCC Nos. 97199, 97200, and 97198;
(b) nucleic acids that hybridize under stringent conditions to the MN nucleic acids of (a); and
(c) nucleic acids that differ from the nucleic acids of (a) or (b) in codon sequence due to the degeneracy of the genetic code. Such isolated nucleic acids, for example, can be polymerase chain reaction (PCR) primers.
The invention further concerns isolated nucleic acids that code for an MN protein, MN fusion protein or MN polypeptide that is operatively linked to an expression control sequence within a vector; unicellular hosts, prokaryotic or eukaryotic, that are transformed or transfected therewith; and methods of recombinantly producing MN proteins, MN fusion proteins and MN polypeptides comprising transforming or transfecting unicellular hosts with said nucleic acid operatively linked to an expression control sequence, culturing said transformed or transfected unicellular hosts so that said MN proteins, fusion proteins or polypeptides are expressed, and extracting and isolating said MN protein fusion protein or polypeptide.
Recombinant nucleic acids that encode MN fusion proteins are claimed as consisting essentially of an MN protein or MN polypeptide and a non-MN protein or polypeptide wherein the nucleotide sequence for the portion of the nucleic acid encoding the MN protein or polypeptide is selected from the group consisting of:
(a) SEQ. ID. NO.: 1;
(b) nucleotide sequences that hybridize under stringent conditions to SEQ. ID. NO.: 1 or to its complement; and
(c) degenerate variants of SEQ. ID. NO.: 1, and of the nucleotide sequences of (b);
wherein the nucleic acid encoding said MN protein or polypeptide contains at least twenty-nine nucleotides.
Said non-MN protein or polypeptide may preferably be nonimmunogenic to humans and not typically reactive to antibodies in human body fluids. Examples of such a DNA sequence is the alpha-peptide coding region of beta-galactosidase and a sequence coding for glutathione S-transferase or a fragment thereof. However, in some instances, a non-MN protein or polypeptide that is serologically active, immunogenic and/or antigenic may be preferred as a fusion partner to a MN antigen. Further, claimed herein are such recombinant fusion proteins/polypeptides which are substantially pure and non-naturally occurring. Exemplary fusion proteins of this invention are GEX-3X-MN, MN-Fc and MN-PA, described infra.
In HeLa and in tumorigenic HeLa x fibroblast hybrid (H/F-T) cells, MN protein is manifested as a "twin" protein p54/58N; it is glycosylated and forms disulfide-linked oligomers. As determined by electrophoresis upon reducing gels, MN proteins have molecular weights in the range of from about 40 kd to about 70 kd, preferably from about 45 kd to about 65 kd, more preferably from about 48 kd to about 58 kd. Upon non-reducing gels, MN proteins in the form of oligomers have molecular weights in the range of from about 145 kd to about 220 kd, preferably from about 150 to about 200 kd, still more preferably from about 150 to about 155 kd, and further preferably from about 152 to about 154 kd. A predicted amino acid sequence for a preferred MN protein of this invention is shown in FIG. 1 [SEQ. ID. NO. 2].
Other particular MN proteins or polypeptides are exemplified by the putative MN signal peptide shown as the first thirty-seven amino acids in FIG. 1 [SEQ. ID. NO.: 6], preferred MN antigen epitopes [SEQ. ID. NOS.: 10-16], and domains of the MN protein represented in FIG. 1 amino acids (aa) 38-414 (SEQ. ID. NO.: 87; the extracellular domain), aa 415-434 (SEQ. ID. NO.: 52; the transmembrane domain), aa 435-459 (SEQ. ID. NO.: 53; the intracellular domain), aa 53-111 (SEQ. ID. NO.: 50; the proteoglycan-like domain); and aa 135-391 (SEQ. ID. NO.: 51; the CA domain).
The invention further relates to the biochemical engineering of the MN gene, fragments thereof or related cDNA. For example, said gene or a fragment thereof or related cDNA can be inserted into a suitable expression vector, wherein it is operatively linked to an expression control sequence; host cells, preferably unicellular, can be transformed or transfected with such an expression vector; and an MN protein/polypeptide, preferably an MN protein, is expressed therein. Such a recombinant protein or polypeptide can be glycosylated or nonglycosylated, preferably glycosylated, and can be purified to substantial purity. The invention further concerns MN proteins/polypeptides which are synthetically or otherwise biologically prepared.
Said MN proteins/polypeptides can be used in assays to detect MN antigen in patient samples and in serological assays to test for MN-specific antibodies. MN proteins/polypeptides of this invention are serologically active, immunogenic and/or antigenic. They can further be used as immunogens to produce MN-specific antibodies, polyclonal and/or monoclonal, as well as an immune T-cell response.
The invention is directed to MN-specific antibodies, which can be used diagnostically/prognostically and may be used therapeutically. Preferred according to this invention are MN-specific antibodies reactive with the epitopes represented respectively by the amino acid sequences of the MN protein shown in FIG. 1 as follows: from aa 62 to aa 67 [SEQ. ID. NO.: 10]; from aa 55 to aa 60 [SEQ. ID. NO.: 11]; from aa 127 to aa 147 [SEQ. ID. NO.: 12]; from aa 36 to aa 51 [SEQ. ID. NO.: 13]; from aa 68 to aa 91 [SEQ. ID. NO.: 14]; from aa 279 to aa 291 [SEQ. ID. NO.: 15]; and from aa 435 to aa 450 [SEQ. ID. NO.: 16]. More preferred are antibodies reactive with epitopes represented by SEQ. ID. NOS.: 10, 11 and 12. Still more preferred are antibodies reactive with the epitopes represented by SEQ. ID NOS: 10 and 11, as for example, respectively Mabs M75 and MN12. Most preferred are monoclonal antibodies reactive with the epitope represented by SEQ. ID. NO.: 10.
Also preferred according to this invention are antibodies prepared against recombinantly produced MN proteins as, for example, GEX-3X-MN, MN 20-19, MN-Fc and MN-PA. Also preferred are MN-specific antibodies prepared against glycosylated MN proteins, such as, MN 20-19 expressed in baculovirus infected Sf9 cells.
A hybridoma that produces a representative MN-specific antibody, the monoclonal antibody M75 (Mab M75), was deposited at the under ATCC Number HB 11128 as indicated above. The M75 antibody was used to discover and identify the MN protein and can be used to identify readily MN antigen in Western blots, in radioimmunoassays and immunohistochemically, for example, in tissue samples that are fresh, frozen, or formalin-, alcohol-, acetone- or otherwise fixed and/or paraffin-embedded and deparaffinized. Another representative MN-specific antibody, Mab MN12, is secreted by the hybridoma MN 12.2.2, which was deposited at the ATCC under the designation HB 11647.
MN-specific antibodies can be used, for example, in laboratory diagnostics, using immunofluorescence microscopy or immunohistochemical staining; as a component in immunoassays for detecting and/or quantitating MN antigen in, for example, clinical samples; as probes for immunoblotting to detect MN antigen; in immunoelectron microscopy with colloid gold beads for localization of MN proteins and/or polypeptides in cells; and in genetic engineering for cloning the MN gene or fragments thereof, or related cDNA. Such MN-specific antibodies can be used as components of diagnostic/prognostic kits, for example, for in vitro use on histological sections; such antibodies can also and used for in vivo diagnostics/prognostics, for example, such antibodies can be labeled appropriately, as with a suitable radioactive isotope, and used in vivo to locate metastases by scintigraphy. Further such antibodies may be used in vivo therapeutically to treat cancer patients with or without toxic and/or cytostatic agents attached thereto. Further, such antibodies can be used in vivo to detect the presence of neoplastic and/or preneoplastic disease. Still further, such antibodies can be used to affinity purify MN proteins and polypeptides.
This invention also concerns methods of treating neoplastic disease and/or preneoplastic disease comprising inhibiting the expression of MN genes by administering antisense nucleic acid sequences that are substantially complementary to mRNA transcribed from MN genes. Said antisense nucleic acid sequences are those that hybridize to such mRNA under stringent hybridization conditions. Preferred are antisense nucleic acid sequences that are substantially complementary to sequences at the 5' end of the MN cDNA sequence shown in FIG. 1. Preferably said antisense nucleic acid sequences are oligonucleotides.
This invention also concerns vaccines comprising an immunogenic amount of one or more substantially pure MN proteins and/or polypeptides dispersed in a physiologically acceptable, nontoxic vehicle, which amount is effective to immunize a vertebrate, preferably a mammal, more preferably a human, against a neoplastic disease associated with the expression of MN proteins. Said proteins can be recombinantly, synthetically or otherwise biologically produced. A particular use of said vaccine would be to prevent recidivism and/or metastasis. For example, it could be administered to a patient who has had an MN-carrying tumor surgically removed, to prevent recurrence of the tumor.
Abbreviations
The following abbreviations are used herein:
aa--amino acid
ATCC--American Type Culture Collection
bp--base pairs
BLV--bovine leukemia virus
BSA--bovine serum albumin
BRL--Bethesda Research Laboratories
CA--carbonic anhydrase
CAM--cell adhesion molecule
CARP--carbonic anhydrase related protein
CAT--chloramphenicol acetyltransferase
Ci--curie
cm--centimeter
CMV--cytomegalovirus
cpm--counts per minute
C-terminus--carboxyl-terminus
.degree. C.--degrees centigrade
DEAE--diethylaminoethyl
DMEM--Dulbecco modified Eagle medium
ds--double-stranded
EDTA--ethylenediaminetetraacetate
EIA--enzyme immunoassay
ELISA--enzyme-linked immunosorbent assay
EMSA--electrophoretic mobility shift assay
F--fibroblasts
FCS--fetal calf serum
FITC--fluorescein isothiocyanate
FTP--DNase 1 footprinting analysis
GEX-3X-MN--fusion protein MN glutathione S-transferase
H--HeLa cells
H-E--haematoxylin-eosin
HEF--human embryo fibroblasts
HeLa K--standard type of HeLa cells
HeLa S--Stanbridge's mutant HeLa D98/AH.2
H/F-T--hybrid HeLa fibroblast cells that are tumorigenic; derived from HeLa D98/AH.2
H/F-N--hybrid HeLa fibroblast cells that are nontumorigenic; derived from HeLa D98/AH.2
HPV--human papilloma virus
HRP--horseradish peroxidase
IC--intracellular
Inr--initiator
IPTG--isopropyl-Beta-D-thiogalacto-pyranoside
kb--kilobase
kbp--kilobase pairs
kd or kDa--kilodaltons
KS--keratan sulphate
LCMV--lymphocytic choriomeningitis virus
LTR--long terminal repeat
M--molar
mA--milliampere
MAb--monoclonal antibody
ME--mercaptoethanol
MEM--minimal essential medium
min.--minute(s)
mg--milligram
ml--milliliter
mM--millimolar
MMC--mitomycin C
mmol--millimole
MLV--murine leukemia virus
N--normal concentration
NEG--negative
ng--nanogram
nm--nanometer
nt--nucleotide
N-terminus--amino-terminus
ODN--oligodeoxynucleotide
ORF--open reading frame
PA--Protein A
PBS--phosphate buffered saline
PCR--polymerase chain reaction
PEST--combination of one-letter abbreviations for proline, glutamic acid, serine, threonine
PG--proteoglycan
pI--isoelectric point
PMA--phorbol 12-myristate 13-acetate
POS--positive
Py--pyrimidine
RACE--rapid amplification of cDNA ends
RIA--radioimmunoassay
RIP--radioimmunoprecipitation
RIPA--radioimmunoprecipitation assay
RNP--RNase protection assay
SAC--Staphylococcus aureus cells
S. aureus--Staphylococcus aureus
Sc--subcutaneous
SDRE--serum dose response element
SDS--sodium dodecyl sulfate
SDS-PAGE--sodium dodecyl sulfate-polyacrylamide gel electrophoresis
SINE--short interspersed repeated sequence
SSDS--synthetic splice donor site
SP--signal peptide
SP-RIA--solid-phase radioimmunoassay
SSDS--synthetic splice donor site
SSPE--NaCl (0.18 M), sodium phosphate (0.01 M), EDTA (0.001 M)
TBE--Tris-borate/EDTA electrophoresis buffer
TCA--trichloroacetic acid
TC media--tissue culture media
TM--transmembrane
TMB--tetramethylbenzidine
Tris--tris (hydroxymethyl) aminomethane
.mu.Ci--microcurie
.mu.g--microgram
.mu.l--microliter
.mu.M--micromolar
VSV--vesicular stomatitis virus
X-MLV--xenotropic murine leukemia virus
Cell Lines
AGS--cell line derived from a primary adenogastric carcinoma [Barranco and Townsend, Cancer Res., 43: 1703 (1983) and Invest. New Drugs, 1: 117 (1983)]; available from the ATCC under CRL-1739;
C33--a cell line derived from a human cervical carcinoma biopsy [Auersperg, N., J. Nat'l. Cancer Inst. (Bethesda), 32: 135-148 (1964)]; available from the ATCC under HTB-31.
HeLa K--standard type of HeLa cells; aneuploid, epithelial-like cell line isolated from a human cervical adenocarcinoma [Gey et al., Cancer Res., 12: 264 (1952); Jones et al., Obstet. Gynecol., 38: 945-949 (1971)] obtained from Professor B. Korych, [Institute of Medical Microbiology and Immunology, Charles University; Prague, Czech Republic];
HeLa D98/AH.2 (also HeLa S)--Mutant HeLa clone that is hypoxanthine guanine phosphoribosyl transferase-deficient (HGPRT.sup.-) kindly provided by Eric J. Stanbridge [Department of Microbiology, College of Medicine, University of California, Irvine, Calif. (USA)] and reported in Stanbridge et al., Science, 215: 252-259 (Jan. 15, 1982); parent of hybrid cells H/F-N and H/F-T, also obtained from E. J. Stanbridge;
KATO III--cell line prepared from a metastatic form of a gastric carcinoma [Sekiguichi et al., Japan J. Exp. Med., 48: 61 (1978)]; available from the ATCC under HTB-103;
NIH-3T3--murine fibroblast cell line reported in Aaronson, Science, 237: 178 (1987); Rat2TK.sup.- --cell line (rat embryo, thymidine kinase mutant) was derived from a subclone of a 5'-bromo-deoxyuridine resistant strain of the Fischer rat fibroblast 3T3-like cell line Rat1; the cells lack appreciable levels of nuclear thymidine kinase [Ahrens, B., i Virology, 113: 408 (1981)];
XC--cells derived from a rat rhabdomyosarcoma induced with Rous sarcoma virus-induced rat sarcoma [Svoboda, J., Natl. Cancer Center Institute Monograph No. 17, IN: "International Conference on Avian Tumor Viruses" (J. W. Beard ed.), pp. 277-298 (1964)], kindly provided by Jan Svoboda [Institute of Molecular Genetics, Czechoslovak Academy of Sciences; Prague, Czech Republic]; and
CGL1--H/F-N hybrid cells (HeLa D98/AH.2 derivative);
CGL2--H/F-N hybrid cells (HeLa D98/AH.2 derivative);
CGL3--H/F-T hybrid cells (HeLa D98/AH.2 derivative);
CGL4--H/F-T hybrid cells (HeLa D98/Ah.2 derivative).
Nucleotide and Amino Acid Sequence Symbols
The following symbols are used to represent nucleotides herein:
There are twenty main amino acids, each of which is specified by a different arrangement of three adjacent nucleotides (triplet code or codon), and which are linked together in a specific order to form a characteristic protein. A three-letter or one-letter convention is used herein to identify said amino acids, as, for example, in FIG. 1 as follows:
BRIEF DESCRIPTION OF THE FIGURES
FIGS. 1A-1C provides the nucleotide sequence for a MN cDNA [SEQ. ID. NO.: 1] clone isolated as described herein. FIG. 1 also sets forth the predicted amino acid sequence [SEQ. ID. NO.: 2] encoded by the cDNA.
FIGS. 2A-F provides a 10,898 bp complete genomic sequence of MN [SEQ. ID. NO.: 5]. The base count is as follows: 2654 A; 2739 C; 2645 G; and 2859 T. The 11 exons are in general shown in capital letters, but exon 1 is considered to begin at position 3507 as determined by RNase protection assay.
FIG. 3 is a restriction map of the full-length MN cDNA. The open reading frame is shown as an open box. The thick lines below the restriction map illustrate the sizes and positions of two overlapping cDNA clones. The horizontal arrows indicate the positions of primers R1 [SEQ. ID. NO.: 7] and R2 [SEQ. ID. NO.: 8] used for the 5' end RACE. Relevant restriction sites are BamHI (B), EcoRV (V), EcoRI (E), PstI (Ps), PvuII (Pv).
FIG. 4 schematically represents the 5' MN genomic region of a MN genomic clone wherein the numbering corresponds to transcription initiation sites estimated by RACE.
FIG. 5 provides an exon-intron map of the human MN/CA IX gene. The positions and sizes of the exons (numbered, cross-hatched boxes), Alu repeat elements (open boxes) and an LTR-related sequence (first unnumbered stippled box) are adjusted to the indicated scale. The exons corresponding to individual MN/CA IX protein domains are enclosed in dashed frames designated PG (proteoglycan-like domain), CA (carbonic anhydrase domain), TM (transmembrane anchor) and IC (intracytoplasmic tail). Below the map, the alignment of amino acid sequences illustrates the extent of homology between the MN/CA IX protein PG region (aa 53-111) [SEQ. ID. NO.: 50] and the human aggrecan (aa 781-839) [SEQ. ID. NO.: 54].
FIG. 6 is a nucleotide sequence for the proposed promoter of the human MN gene [SEQ. ID. NO.: 27]. The nucleotides are numbered from the transcription initiation site according to RNase protection assay. Potential regulatory elements are overlined. Transcription start sites are indicated by asterisks (RNase protection) and dots (RACE) above the corresponding nucleotides. The sequence of the 1st exon begins under the asterisks. FTP analysis of the MN4 promoter fragment revealed 5 regions (I-V) protected at both the coding and noncoding strands, and two regions (VI and VII) protected at the coding strand but not at the noncoding strand.
FIG. 7 provides a schematic of the alignment of MN genomic clones according to their position related to the transcription initiation site. All the genomic fragments except Bd3 were isolated from a lambda FIX II genomic library derived from HeLa cells. Clone Bd3 was derived from a human fetal brain library.
FIG. 8 schematically represents the MN protein structure. The abbreviations are the same as used in FIG. 5. The scale indicates the number of amino acids.
FIG. 9 outlines an experiment designed to explain the mechanism of reversion of NIH3T3 cells transformed with the MN coding sequence (pGD.MN) .
DETAILED DESCRIPTION
The MN gene is shown herein to be organized into 11 exons and 10 introns. Described herein is the cloning and sequencing of the MN cDNA and genomic sequences, and the genetic engineering of MN proteins--such as the GEX-3X-MN, MN-PA, MN-Fc and MN 20-19 proteins. The recombinant MN proteins can be conveniently purified by affinity chromatography.
MN/CA IX was first identified in HeLa cells, derived from human carcinoma of cervix uteri, as both a plasma membrane and nuclear protein with an apparent molecular weight of 58 and 54 kilodaltons (kDA) as estimated by Western blotting. It is N-glycosylated with a single 3kDa carbohydrate chain and under non-reducing conditions forms S-S-linked oligomers [Pastorekova et al., Virology, 187: 620-626 (1992); Pastorek et al., Oncogene, 9: 2788-2888 (1994)]. MN/CA IX is a transmembrane protein located at the cell surface, although in some cases it has been detected in the nucleus [Zavada et al., Int. J. Cancer, 54: 268-274 (1993); Pastorekova et al., supra].
MN is manifested in HeLa cells by a twin protein, p54/58N. Immunoblots using a monoclonal antibody reactive with p54/58N (MAb M75) revealed two bands at 54 kd and 58 kd. Those two bands may correspond to one type of protein that most probably differs by post-translational processing. Herein, the phrase "twin protein" indicates p54/58N.
The expression of MN proteins appears to be diagnostic/prognostic for preneoplastic/neoplastic disease. The MN twin protein, p54/58N, was found to be expressed in HeLa cells and in Stanbridge's tumorigenic (H/F-T) hybrid cells [Stanbridge et al., Somatic Cell Genet, 7: 699-712 (1981); and Stanbridge et al., Science, 215: 252-259 (1982)] but not in fibroblasts or in non-tumorigenic (H/F-N) hybrid cells [Stanbridge et al., id.]. In early studies reported in Zavada et al. WO 93/18152, supra, MN proteins were found in immunoblots prepared from human ovarian, endometrial and uterine cervical carcinomas, and in some benign neoplasias (as mammary papilloma) but not from normal ovarian, endometrial, uterine or placental tissues.
Example 1 herein details further research on MN gene expression wherein MN antigen, as detected by immunohistochemical staining, was found to be prevalent in tumor cells of a number of cancers, including cervical, bladder, head and neck, and renal cell carcinomas among others. Further, the immunohistochemical staining experiments of Example 1 show that among normal tissues tested, only normal stomach tissues showed routinely and extensively the presence of MN antigen. MN antigen is further shown herein to be present sometimes in morphologically normal-appearing areas of tissue specimens exhibiting dysplasia and/or malignancy. Examples 4-7 show further evidence of abnormal MN gene expression in gastrointestinal tract and related tissues that are indicative of oncogenesis in those tissues.
MN Gene--Cloning and Sequencing
FIGS. 1A-C provides the nucleotide sequence for a full-length MN cDNA clone isolated as described below [SEQ. ID. NO.: 1]. FIG. 2A-F provides a complete MN genomic sequence [SEQ. ID. NO.: 5]. FIG. 6 shows the nucleotide sequence for a proposed MN promoter [SEQ. ID. NO.: 27].
It is understood that because of the degeneracy of the genetic code, that is, that more than one codon will code for one amino acid [for example, the codons TTA, TTG, CTT, CTC, CTA and CTG each code for the amino acid leucine (leu)], that variations of the nucleotide sequences in, for example, SEQ. ID. NOS.: 1 and 5 wherein one codon is substituted for another, would produce a substantially equivalent protein or polypeptide according to this invention. All such variations in the nucleotide sequences of the MN cDNA and complementary nucleic acid sequences are included within the scope of this invention.
It is further understood that the nucleotide sequences herein described and shown in FIGS. 1, 2 and 6, represent only the precise structures of the cDNA, genomic and promoter nucleotide sequences isolated and described herein. It is expected that slightly modified nucleotide sequences will be found or can be modified by techniques known in the art to code for substantially similar or homologous MN proteins and polypeptides, for example, those having similar epitopes, and such nucleotide sequences and proteins/polypeptides are considered to be equivalents for the purpose of this invention. DNA or RNA having equivalent codons is considered within the scope of the invention, as are synthetic nucleic acid sequences that encode proteins/polypeptides homologous or substantially homologous to MN proteins/polypeptides, as well as those nucleic acid sequences that would hybridize to said exemplary sequences [SEQ. ID. NOS. 1, 5 and 27] under stringent conditions, or that, but for the degeneracy of the genetic code would hybridize to said cDNA nucleotide sequences under stringent hybridization conditions. Modifications and variations of nucleic acid sequences as indicated herein are considered to result in sequences that are substantially the same as the exemplary MN sequences and fragments thereof.
Partial cDNA clone
In Zavada et al., id., the isolation of a partial MN cDNA clone of 1397 bp in length was described. A lambda gt11 cDNA library of LMCV-infected HeLa cells was prepared and subjected to immunoscreening with Mab M75 in combination with goat anti-mouse antibodies conjugated with alkaline phosphatase. One positive clone was picked and subcloned into the NotI site of pBlusecript KS [Stratagen; La Jolla, Calif. (USA)] thereby creating pBluscript-MN.
Two oppositely oriented nested deletions were made using Erase-a-Base.TM. kit [Promega; Madison, Wis. (USA)] and sequenced by dideoxy method with a T7 sequencing kit [Pharmacia; Piscataway, N.J. (USA)]. The sequencing showed a partial cDNA clone, the insert being 1397 bp long. The sequence comprises a large 1290 bp open reading frame and 107 bp 3' untranslated region containing a polyadenylation signal (AATAAA). However, the sequence surrounding the first ATG codon in the open reading frame (ORF) did not fit the definition of a translational start site. In addition, as followed from a comparison of the size of the MN clone with that of the corresponding mRNA in a Northern blot, the cDNA was shown to be missing about 100 bp from the 5' end of its sequence.
Full-Length cDNA Clone
Attempts to isolate a full-length clone from the original cDNA library failed. Therefore, the inventors performed a rapid amplification of cDNA ends (RACE) using MN-specific primers, R1 and R2 [SEQ. ID. NOS.: 7 and 8], derived from the 5' region of the original cDNA clone. The RACE product was inserted into pBluescript, and the entire population of recombinant plasmids was sequenced with an MN-specific primer ODN1 [SEQ. ID. NO.: 3]. In that way, a reliable sequence at the very 5' end of the MN cDNA as shown in FIG. 1 [SEQ. ID. NO.: 1] was obtained.
Specifically, RACE was performed using 5' RACE System [GIBCO BRL; Gaithersburg, Md. (USA)] as follows. 1 .mu.g of mRNA (the same as above) was used as a template for the first strand cDNA synthesis which was primed by the MN-specific antisense oligonucleotide, R1 (5'-TGGGGTTCTTGAGGATCTCCAGGAG-3') [SEQ. ID. NO.: 7]. The first strand product was precipitated twice in the presence of ammonium acetate and a homopolymeric C tail was attached to its 3' end by TdT. Tailed cDNA was then amplified by PCR using a nested primer, R2 (5'-CTCTAACTTCAGGGAGCCCTCTTCTT-3') [SEQ. ID. NO.: 8] and an anchor primer that anneals to the homopolymeric tail (5'-CUACUACUACUAGGCCACGCGTCGACTAGTACGGGI IGGGIIGGGIIG-3') [SEQ. ID. NO.: 9]. The amplified product was digested with BamHI and SalI restriction enzymes and cloned into pBluescript II KS plasmid. After transformation, plasmid DNA was purified from the whole population of transformed cells and used as a template for sequencing with the MN-specific primer ODN1 [SEQ. ID. NO.: 3; a 29-mer 5' CGCCCAGTGGGTCATCTTCCCCAGAAGAG 3'].
Based upon results of the RACE analysis, the full-length MN cDNA sequence was seen to contain a single ORF starting at position 12, with an ATG codon that is in a good context (GCGCATGG) with the rule proposed for translation initiation [Kozak, J. Cell. Biol., 108: 229-241 (1989)]. The AT rich 3' untranslated region contains a polyadenylation signal (AATAAA) preceding the end of the cDNA by 10 bp. Surprisingly, the sequence from the original clone as well as from four additional clones obtained from the same cDNA library did not reveal any poly(A) tail. Moreover, just downstream of the poly(A) signal, an ATTTA motif that is thought to contribute to mRNA instability [Shaw and Kamen, Cell, 46: 659-667 (1986)] was found. That fact raised the possibility that the poly (A) tail is missing due to the specific degradation of the MN mRNA.
Genomic clones
To study MN regulation, MN genomic clones were isolated. One MN genomic clone (Bd3) was isolated from a human cosmid library prepared from fetal brain using both MN cDNA as a probe and the MN-specific primers derived from the 5' end of the cDNA ODN1 [SEQ. ID. NO.: 3, supra] and ODN2 [SEQ. ID NO.: 4; 19-mer (5' GGAATCCTCCTGCATCCGG 3')]. Sequence analysis revealed that that genomic clone covered a region upstream from a MN transcription start site and ending with the BamHI restriction site localized inside the MN cDNA. Other MN genomic clones can be similarly isolated.
In order to identify the complete genomic region of MN, the human genomic library in Lambda FIX II vector (Stratagene) was prepared from HeLa chromosomal DNA and screened by plaque hybridization using MN cDNA as described below. Several independent MN recombinant phages were identified, isolated and characterized by restriction mapping and hybridization analyses. Four overlapping recombinants covering the whole genomic region of MN were selected, digested and subcloned into pBluescript. The subclones were then subjected to bidirectional nested deletions and sequencing. DNA sequences were compiled and analyzed by computer using the DNASIS software package.
FIG. 7 provides a schematic of the alignment of MN genomic clones according to the transcription initiation site. Plasmids containing the A4a clone and the XE1 and XE3 subclones were deposited at the American Type Culture Collection (ATCC) at 12301 Parklawn Drive, Rockville, Md. 20852 (USA) on Jun. 6, 1995, respectively under ATCC Deposit Nos. 97199, 97200, and 97198.
Exon-Intron Structure of Complete MN Genomic Region
The complete sequence of the overlapping clones contains 10,898 bp (SEQ. ID. NO.: 5). FIG. 5 depicts the organization of the human MN gene, showing the location of all 11 exons as well as the 2 upstream and 6 intronic Alu repeat elements. All the exons are small, ranging from 27 to 191 bp, with the exception of the first exon which is 445 bp. The intron sizes range from 89 to 1400 bp.
Table 1 below lists the splice donor and acceptor sequences that conform to consensus splice sequences including the AG-GT motif [Mount, Nucleic Acids Res. 10: 459-472 (1982)].
The CA domain is encoded by exons 2-8, while the exons 1, 10 and 11 correspond respectively to the proteoglycan-like domain, the transmembrane anchor and cytoplasmic tail of the MN/CA IX protein. That structure suggests that MN is a chimeric gene assembled by exon shuffling. The gene diverged from an ancestral CA gene at a relatively early stage of evolution as indicated by the intron distribution in the CA domain coding region as well as by amino acid sequence homology.
The exon/intron pattern of CA coding region of MN/CA IX is closer to that of CA IV gene that encodes a membrane-associated isoenzyme than of genes corresponding to cytoplasmic and mitochondrial isoenzymes. However, based on amino acid sequence homology, MN/CA IX is more closely related to the secreted CA VI than to any other isoenzyme. Since CA IV, CA VI and CARP/CA VIII are thought to have diverged the earliest, CA VII and CA V somewhat later and CAs I, II, III more recently [Tashian, R. E., Adv. in Genetics, 30: 321-356 (1992)], it appears that MN/CA IX belongs to the oldest mammalian CA genes.
The structure of the genomic region coding for the CA domain of MN/CA IX is similar in possessing seven exons, to other CA genes characterized so far, except for CA I and CA IV genes that have an additional exon at their 5' end [Lowe et al., Gene, 93: 277-283 (1990); Okuyama et al., Genomics, 16: 678-684 (1993).] In the cytosolic and mitochondrial CA genes (CA I, II, III, V and VII, six introns are distributed at identical positions. The CA IV gene, encoding the membrane-bound isoenzyme, shares positions of only three 3' introns (introns 3, 4 and 6) with the cytosolic and mitochondrial CAs. The fourth position (intron 5) shows a 1 bp slippage at both the donor and acceptor sites. The remaining introns involve either separate insertion events or considerable slippage with little or no change in polypeptide length. Alignment of human CAs, whose gene structure has already been determined, shows with respect to the placement of introns 2 and 5, MN/CA IX is more similar to CA IV, than to CA I, II, III, V, and VII. However, the position of intron 1 appears closer to that of CA I, II, III, V and VII. Generally, the coding sequence of the CA domain of the MN/CA IX protein is divided in a manner analogous to sequences of other CA genes. That fact supports the view that MN/CA IX belongs to the CA gene family.
Mapping of MN Gene Transcription Initiation Site
In the earlier attempt to localize the site of transcription initiation of the MN gene by RACE (above), obtained was a major PCR fragment whose sequence placed the start site 12 bp upstream from the first codon of the ORF. That result was obtained probably due to a preferential amplification of the shortest form of mRNA. Therefore, the inventors used an RNase protection assay (RNP) for fine mapping of the 5' end of the MN gene. The probe was a uniformly labeled 470 nucleotide copy RNA (nt -205 to +265) [SEQ. ID. NO.: 55], which was hybridized to total RNA from MN-expressing HeLa and CGL3 cells and analyzed on a sequencing gel. That analysis has shown that the MN gene transcription initiates at multiple sites, the 5' end of the longest MN transcript being 30 nt longer than that previously characterized by RACE.
Mapping of MN Gene Transcription Termination Site
An RNase protection assay was used to verify the 3' end of the MN cDNA. That was important with respect to our previous finding that the cDNA contains a poly(A) signal but lacks a poly(A) tail, which could be lost during the proposed degradation of MN mRNA due to the presence of an instability motif in its 3' untranslated region. RNP analysis of MN mRNA with the fragment of the genomic clone XE3 covering the region of interest corroborated our data from MN cDNA sequencing, since the 3' end of the protected fragment corresponded to the last base of MN cDNA (position 10,752 of the genomic sequence). That site also meets the requirement for the presence of a second signal in the genomic sequence that is needed for transcription termination and polyadenylation [McLauchlan et al., Nucleic Acids Res., 13: 1347 (1985)]. Motif TGTGTTAGT (nt 10,759-10,767) corresponds well to both the consensus sequence and the position of that signal within 22 bp downstream from the polyA signal (nt 10,737-10,742).
Characterization of the 5' Flanking Region
The Bd3 genomic clone isolated from human fetal brain cosmid library was found to cover a region of 3.5 kb upstream from the transcription start site of the MN gene. It contains no significant coding region. Two Alu repeats are situated at positions -2587 to -2296 [SEQ. ID. NO.: 56] and -1138 to -877 [SEQ. ID. NO.: 57] (with respect to the transcription start determined by RNP). The sequence proximal to the 5' end is strongly homologous (91.4% identity) to the U3 region of long terminal repeats of human endogenous retroviruses HERV-K [Ono, M., J. Virol, 58: 937-944 (1986)]. The LTR-like fragment is 222 bp long with an A-rich tail at its 3' end. Most probably, it represents part of SINE (short interspersed repeated sequence) type nonviral retroposon derived from HERV-K [Ono et al., Nucleic Acids Res., 15: 8725-8373 (1987)]. There are no sequences corresponding to regulatory elements in this fragment, since the 3' part of U3, and the entire R and US regions of LTR are absent from the Bd3 genomic clone, and the glucocorticoid responsive element as well as the enhancer core sequences are beyond its 5' border.
However, two keratinocyte-dependent enhancers were identified in the sequence downstream from the LTR-like fragment at positions -3010 and -2814. Those elements are involved in transcriptional regulation of the E6-E7 oncogenes of human papillomaviruses and are thought to account for their tissue specificity [Cripe et al., EMBO J., 6: 3745-3753 (1987)].
Nucleotide sequence analysis of the DNA 5' to the transcription start (from nt -507) revealed no recognizable TATA box within the expected distance from the beginning of the first exon. However, the presence of potential binding sites for transcription factors suggests that this region might contain a promoter for the MN gene. There are several consensus sequences for transcription factors AP1 and AP2 as well as for other regulatory elements, including a p53 binding site [Locker and Buzard, J., DNA Sequencing and Mapping, 1: 3-11 (1990); Imagawa et al. Cell, 51: 251-260 (1987); E1 Deiry et al., Nat. Genet., 1: 44-49 (1992)]. Although the putative promoter region contains 59.3% C+G, it does not have additional attributes of CpG-rich islands that are typical for TATA-less promoters of housekeeping genes [Bird, Nature, 321: 209-213 (1986)]. Another class of genes lacking TATA box utilizes the initiator (Inr) element as a promoter. Many of these genes are not constitutively active, but they are rather regulated during differentiation or development. The Inr has a consensus sequence of PyPyPyCAPyPyPyPyPy [SEQ. ID. NO.: 23] and encompasses the transcription start site [Smale and Baltimore, Cell, 57: 103-113 (1989)]. There are two such consensus sequences in the MN putative promoter; however, they do not overlap the transcription start (FIG. 6).
An interesting region was found in the middle of the MN gene. The region is about 1.4 kb in length [nt 4,600-6,000 of the genomic sequence; SEQ. ID. NO.: 49] and spans from the 3' part of the 1st intron to the end of the 5th exon. The region has the character of a typical CpG-rich island, with 62.8% C+G content and 82 CpG: 131 GpC dinucleotides. Moreover, there are multiple putative binding sites for transcription factors AP2 and Sp1 [Locker and Buzard, supra; Briggs et al., Science, 234: 47-52 (1986)] concentrated in the center of this area. Particularly the 3rd intron of 131 bp in length contains three Sp1 and three AP2 consensus sequences. That data indicates the possible involvement of that region in the regulation of MN gene expression. However, functionality of that region, as well as other regulatory elements found in the proposed 5' MN promoter, remains to be determined.
MN Promoter
Study of the MN promoter has shown that it is TATA-less and contains regulatory sequences for AP-1, AP-2, as well as two p53 binding sites. The sequence of the 5' end of the 3.5 kb flanking region upstream of the MN gene has shown extensive homology to LTR of HERV-K endogenous retroviruses. Basal transcription activity of the promoter is very weak as proven by analyses using CAT and neo reporter genes. However, expression of the reporter genes is severalfold increased when driven from the 3.5 kb flanking region, indicating involvement of putative enhancers.
MN Promoter Analysis
Since the MN promoter is weak, a classical approach to study it would be limited due to the relatively low efficiency of transient transfections (up to 10%). Therefore, stable clonal cell lines expressing constructs containing the MN promoter fused to the CAT gene were prepared. In such clonal lines, 100% of the cells express the CAT gene driven from the MN promoter, and thus, the activity of the promoter is detectable easier than in transient experiments. Also, the promoter activity can be analysed repeatedly in the same cells under different conditions or treated by different factors and drugs. This approach allows for the study of the mechanisms underlying MN regulation at the level of transcription initiation.
Several types of transfections with promoter constructs linked to a reporter CAT gene (calcium precipitation, DEAE dextran combined with DMSO shock and/or chloroquine, as well as electroporation), different methods of CAT activity assay (scintillation method, thin layer chromatography) and several recipient cell lines differing in the level of MN expression and in transfection efficiency (HeLa, SiHa, CGL3, KATO III, Rat2TK.sup.- and C33 cells). Activity of the MN promoter was detected preferably by the electroporation of CGL3 cells and thin layer chromatography. Further preferably, C33 cells cotransfected with MN promoter-CAT constructs and pSV2neo were used.
1. To detect basal activity of the MN promoter and to estimate the position of the core promoter, expression of the CAT gene from constructs pMN1 to pMN7 after transfection to CGL3 cells was analyzed. Plasmids with progressive 5' deletions were transfected into CGL3 cells and activity was analyzed by CAT assay. [8 .mu.g of DNA was used for transfection in all cases except pBLV-LTR (2 .mu.g).]
Only very weak CAT activity was detected in cells transfected by pMN1 and pMN2 (containing respectively 933 bp and 600 bp of the promoter sequence). A little higher activity was exhibited with the constructs pMN3, pMN4 and pMN6 (containing respectively 446 bp, 243 bp and 58 bp of the promoter). A slight peak of activity was obtained with pMN5 (starting at position -172 with respect to the transcription start.) Thus, the function of the MN core promoter can be assigned to a region of approximately 500 bp immediately upstream from the MN transcription initiation site.
Interestingly, the activity of the large Bd3 region (covering 3.5 kbp upstream of the transcription start) was severalfold higher than the activity of the core promoter. However, its level was still much lower than that exhibited by a positive control, i.e., BLV-LTR transactivated by Tax, and even lower than the activity of BLV-LTR without transactivation. That the activity of Bd3 was elevated in comparison to the core promoter suggests the presence of some regulatory elements. Such elements are most probably situated in the sequence between pMN1 and Bd3 (i.e. from -1 kbp to -3.5 kbp) [SEQ. ID. NO.: 58]. The cloning and transfection of several deletion versions of Bd3 covering the indicated region can be used to determine the location of the putative regulatory elements.
Similar results were obtained from transfecting KATO III cells with Bd3 and pMN4. The transfected cells expressed a lower level of MN than the CGL3 cells. Accordingly, the activity of the MN promoter was found to be lower than in CGL3 cells.
2. In a parallel approach to study the MN promoter, an analysis based on G418 selection of cells transfected by plasmids containing the promoter of interest cloned upstream from the neo gene was made. This approach is suitable to study weak promoters, since its sensitivity is much higher than that of a standard CAT assay. The principle underlying the method is as follows: an active promoter drives expression of the neo gene which protects transfected cells from the toxic effect of G418, whereas an inactive promoter results in no neo product being made and the cells transfected thereby die upon the action of G418. Therefore, the activity of the promoter can be estimated according to the number of cell colonies obtained after two weeks of selection with G418. Three constructs were used in the initial experiments--pMN1neo, pMN4neo and pMN7neo. As pMN7neo contains only 30 bp upstream of the transcription start site, it was considered a negative control. As a positive control, pSV2neo with a promoter derived from SV40 was used. Rat2TK cells were chosen as the recipient cells, since they are transfectable with high efficiency by the calcium precipitation method.
After transfection, the cells were subjected to two weeks of selection. Then the medium was removed, the cells were rinsed with PBS, and the colonies were rendered visible by staining with methylene blue. The results obtained from three independent experiments corroborated the data from the CAT assays. The promoter construct pMN4neo exhibited higher transcriptional activity than pMN1neo. However, the difference between the positive control and pMN4neo was not so striking as in the CAT assay. That may have been due to both lower promoter activity of pSv2neo compared to Tax-transactivated pBLV-LTR and to different conditions for cell growth after transfection. From that point of view, stable transfection is probably more advantageous for MN expression, since the cells grow in colonies with close cell to cell contact, and the experiment lasts much longer, providing a better opportunity to detect promoter activity.
3. Stable transfectants expressing MN promoter-CAT chimeric genes were prepared by the cotransfection of relevant plasmids with pSV2neo. As recipient cells, HeLa cells were used first. However, no clones expressing the promoter-CAT constructs were obtained. That negative result was probably caused by homologic recombination of the transfected genomic region of MN (e.g. the promoter) with the corresponding endogenous sequence. On the basis of that experience, C33 cells derived from a HPV-negative cervical carcinoma were used. C33 cells do not express MN, since during the process of tumorigenesis, they lost genetic material including chromosomal region 9p which contains the MN gene. In these experiments, the absence of the MN gene may represent an advantage as the possibility of homologic recombinations is avoided.
C33 Cells Transfected with MN Promoter-CAT Constructs
C33 cells expressing the CAT gene under MN promoter regions Bd3 (-3500/+31) [SEQ. ID. NO.: 90] and MN5 (-172/+31) [SEQ. ID. NO.: 91] were used for initial experiments to analyze the influence of cell density on the transcriptional activity of the MN promoter. The results indicated that signals generated after cells come into close contact activate transcription of the CAT protein from the MN promoter in proportion to the density of the cell culture. Interestingly, the data indicated that the MN protein is not required for this phase of signal transduction, since the influence of density is clearly demonstrated in MN-negative C33 cells. Rather, it appears that MN protein acts as an effector molecule produced in dense cells in order to perform a certain biological function (i.e., to perturb contact inhibition). Also interestingly, the MN promoter activity is detectable even in very sparse cell cultures suggesting that MN is expressed at a very low level also is sparse subconfluent culture.
Deletion Variants. Deletion variants of the Bd3-CAT promoter construct were then prepared. The constructs were cotransfected with pSv2neo into C33 cervical cells. After selection with G418, the whole population of stably transfected cells were subjected to CAT ELISA analysis. Expression of the deletion constructs resulted in the synthesis of similar levels of CAT protein to that obtained with the Bd3-CAT construct. On the basis of that preliminary data, the inventors propose that sequences stimulating transcription of MN are located between -3506 and -3375 bp [SEQ. ID. NO.: 92] upstream from the transcription start. That is the sequence exhibiting homology to HERV-K LTR.
Interaction of Nuclear Proteins with MN Promoter Sequences
In order to identify transcription factors binding to the MN promoter and potentially regulating its activity, a series of analyses using an electrophoretic mobility shift assay (EMSA) and DNase I footprinting analysis (FTP) were performed.
EMSA
In the EMSA, purified promoter fragments MN4 (-243/+31) [SEQ. ID. NO.: 93], MN5 (-172/+31) [SEQ. ID. NO.: 91], MN6 (-58/+31) [SEQ. ID. NO.: 94] and pMN7 (-30/+31) [SEQ. ID. NO.: 95], labeled at the 3' ends by Klenow enzyme, were allowed to interact with proteins in nuclear extracts prepared from CGL1 and CGL3 cells. [40 .mu.g of nuclear proteins were incubated with 30,000 cpm end-labeled DNA fragments in the presence of 2 .mu.g poly(dldC).] DNA-protein complexes were analysed by PAGE (native 6%), where the complexes created extra bands that migrated more slowly than the free DNA fragments, due to the shift in mobility which is dependent on the moiety of bound protein.
The EMSA of the MN4 and MN5 promoter fragments revealed several DNA-protein complexes; however, the binding patterns obtained respectively with CGL1 and CGL3 nuclear extracts were not identical. There is a single CGL-1 specific complex.
The EMSA of the MN6 promoter fragment resulted in the formation of three identical complexes with both CGL1 and CGL3 nuclear extracts, whereas the MN7 promoter fragment did not bind any nuclear proteins.
The EMSA results indicated that the CGL1 nuclear extract contains a specific factor, which could participate in the negative regulation of MN expression in CGL1 cells. Since the specific DNA-protein complex is formed with MN4 (-243/+31) [SEQ. ID NO.: 93] and MN5 (-172/+31) [SEQ. ID NO.: 91] promoter fragments, but not with MN6 (-58/+31) [SEQ. ID. NO.: 94], it appears that the binding site of the protein component of that specific complex is located between -173 and -58 bp [SEQ. ID NO.: 96] with respect to transcription initiation.
FTP
To determine the precise location of cis regulatory elements that participate in the transcriptional regulation of the MN gene, FTP was used. Proteins in nuclear extracts prepared respectively from CGL1 and CGL3 cells were allowed to interact with a purified double-stranded (ds) DNA fragment of the MN promoter (MN4, -243/+31) [SEQ. ID. NO.: 931 which was labeled at the 5' end of one strand. [MN4 fragments were labeled either at Xho1 site (-243/+31*) or at Xba1 site (*-243/+31).] The DNA-protein complex was then subjected to DNase I attack, which causes the DNA chain to break at certain bases if they are not in contact with proteins. [A control used BSA instead of DNase.] Examination of the band pattern of the denatured DNA after gel electrophoresis [8% denaturing gel] indicates which of the bases on the labeled strand were protected by protein.
FTP analysis of the MN4 promoter fragment revealed 5 regions (I-V) protected at both the coding and noncoding strand, as well as two regions (VI and VII) protected at the coding strand but not at the noncoding strand. FIG. 6 indicates the general regions on the MN promoter that were protected.
The sequences of the identified protected regions (PR) were subjected to computer analysis using the SIGNALSCAN program to see if they corresponded to known consensus sequences for transcription factors. The data obtained by that computer analyses are as follows:
PR I--coding strand--AP-2, p53, GAL4
noncoding strand--JCV-repeated
PR II--coding strand--AP-1, CGN4
noncoding strand--TCF-1, dFRA, CGN4
PR III--coding strand--no known consensus sequence, only
partial overlap of AP1
noncoding strand--2 TCF-1 sites
PR IV--coding strand--TCF-1, ADR-1
noncoding strand--CTCF, LF-A1, LBP-1
PR V--coding strand--no known consensus motif
noncoding strand--JCV-repeated
PR VI--coding strand--no known consensus motif
noncoding strand--T antigen of SV 40, GAL4
PR VII--coding strand--NF-uE4, U2snRNA.2
noncoding strand--AP-2, IgHC.12, MyoD.
In contrast to EMSA, the FTP analysis did not find any differences between CGL1 and CGL3 nuclear extracts. However, the presence of specific DNA-protein interactions detected in the CGL1 nuclear extracts by EMSA could have resulted from the binding of additional protein to form DNA protein-protein complex. If that specific protein did not contact the DNA sequence directly, its presence would not be detectable by FTP.
EMSA Supershift analysis
The results of the FTP suggests that transcription factors AP-1, AP-2 as well as tumor suppressor protein p53 are potentially involved in the regulation of MN expression. To confirm binding of those particular proteins to the MN promoter, a supershift analysis using antibodies specific for those proteins was performed. For this analysis, DNA-protein complexes prepared as described for EMSA were allowed to interact with MAbs or polyclonal antibodies specific for proteins potentially included in the complex. The binding of antibody to the corresponding protein results in an additional shift (supershift) in mobility of the DNA-protein-antibody complex which is PAGE visualized as an additional, more slowly migrating band.
By this method, the binding of AP-2 to the MN promoter was confirmed. However, this method did not evidence binding of the AP-1 transcription factor. It is possible that MN protein binds AP-1-related protein, which is antigenically different from the AP-1 recognized by the antibodies used in this assay.
Also of high interest is the possible binding of the p53 tumor suppressor protein to the MN promoter. It is well known that wt p53 functions as a transcription factor, which activates expression of growth-restricting genes and down-modulates, directly or indirectly, the expression of genes that are required for ongoing cell proliferation. Transient co-transfection experiments using the pMN4-CAT promoter construct in combination with wt p53 cDNA and mut p53 cDNA, respectively, suggested that wt p53, but not mut p53, negatively regulates expression of MN. In addition, one of two p53-binding sites in the MN promoter is protected in FTP analysis (FIG. 6), indicating that it binds to the corresponding protein. Therefore, supershift analysis to prove that p53 binds to the MN promoter with two p53-specific antibodies, e.g. Mabs 421 and DO-1 [the latter kindly provided by Dr. Vojtesek from Masaryk Memorial Cancer Institute in Brno, Czech Republic] are to be performed with appropriate nuclear extracts, e.g. from MCF-7 breast carcinoma cells which express wt p53 at a sufficient level.
Deduced Amino Acid Sequence
The ORF of the MN cDNA shown in FIG. 1 has the coding capacity for a 459 amino acid protein with a calculated molecular weight of 49.7 kd. The overall amino acid composition of the MN/CA IX protein is rather acidic, and predicted to have a pI of 4.3. Analysis of native MN/CA IX protein from CGL3 cells by two-dimensional electrophoresis followed by immunoblotting has shown that in agreement with computer prediction, the MN/CA IX is an acidic protein existing in several isoelectric forms with pIs ranging from 4.7 to 6.3.
As assessed by amino acid sequence analysis, the deduced primary structure of the MN protein can be divided into four distinct regions. The initial hydrophobic region of 37 amino acids (aa) corresponds to a signal peptide. The mature protein has an N-terminal or extracellular part of 377 amino acids [aa 38-414 (SEQ. ID. NO.: 87], a hydrophobic transmembrane segment of 20 amino acids [aa 415-434 (SEQ. ID. NO.: 52)] and a C-terminal region of 25 amino acids [aa 435-459 (SEQ. ID. NO.: 53)].
The extracellular part is composed of two distinct domains: (1) a proteoglycan-like domain [aa 53-111 (SEQ. ID. NO.: 50)]; and (2) a CA domain, located close to the plasma membrane [aa 135-391 (SEQ. ID. NO.: 51)]. [The amino acid numbers are keyed to those of FIG. 1.]
More detailed insight into MN protein primary structure disclosed the presence of several consensus sequences. One potential N-glycosylation site was found at position 346 of FIG. 1. That feature, together with a predicted membrane-spanning region are consistent with the results, in which MN was shown to be an N-glycosylated protein localized in the plasma membrane. MN protein sequence deduced from cDNA was also found to contain seven S/TPXX sequence elements [SEQ. ID. NOS.: 25 AND 26] (one of them is in the signal peptide) defined by Suzuki, J. Mol. Biol., 207: 61-84 (1989) as motifs frequently found in gene regulatory proteins. However, only two of them are composed of the suggested consensus amino acids.
Experiments have shown that the MN protein is able to bind zinc cations, as shown by affinity chromatography using Zn-charged chelating sepharose. MN protein immunoprecipitated from HeLa cells by Mab M75 was found to have weak catalytic activity of CA. The CA-like domain of MN has a structural predisposition to serve as a binding site for small soluble domains. Thus, MN protein could mediate some kind of signal transduction.
MN protein from LCMV-infected HeLA cells was shown by using DNA cellulose affinity chromatography to bind to immobilized double-stranded salmon sperm DNA. The binding activity required both the presence of zinc cations and the absence of a reducing agent in the binding buffer.
Sequence Similarities
Computer analysis of the MN cDNA sequence was carried out using DNASIS and PROSIS (Pharmacia Software packages). GenBank, EMBL, Protein Identification Resource and SWISS-PROT databases were searched for all possible sequence similarities. In addition, a search for proteins sharing sequence similarities with MN was performed in the MIPS databank with the FastA program [Pearson and Lipman, PNAS (USA), 85: 2444 (1988)].
The proteoglycan-like domain [aa 53-111 (SEQ. ID. NO.: 50)], which is between the signal peptide and the CA domain, shows significant homology (38% identity and 44% positivity) with a keratan sulphate attachment domain of a human large aggregating proteoglycan aggrecan [Doege et al., J. Biol. Chem., 266: 894-902 (1991)].
The CA domain [aa 135-391 (SEQ. ID. NO.: 51)] is spread over 265 aa and shows 38.9% amino acid identity with the human CA VI isoenzyme [Aldred et al., Biochemistry, 30: 569-575 (1991)]. The homology between MN/CA IX and other isoenzymes is as follows: 35.2% with CA II in a 261 aa overlap [Montgomery et al., Nucl. Acids. Res., 15: 4687 (1987)], 31.8% with CA I in a 261 aa overlap [Barlow et al., Nucl. Acids Res., 15: 2386 (1987)], 31.6% with CA IV in a 266 aa overlap [Okuyama et al., PNAS (USA) 89: 1315-1319 (1992)], and 30.5% with CA III in a 259 aa overlap (Lloyd et al., Genes. Dev., 1: 594-602 (1987)].
In addition to the CA domain, MN/CA IX has acquired both N-terminal and C-terminal extensions that are unrelated to the other CA isoenzymes. The amino acid sequence of the C-terminal part, consisting of the transmembrane anchor and the intracytoplasmic tail, shows no significant homology to any known protein sequence.
The MN gene was clearly found to be a novel sequence derived from the human genome. The overall sequence homology between the cDNA MN sequence and cDNA sequences encoding different CA isoenzymes is in a homology range of 48-50% which is considered by ones in the art to be low. Therefore, the MN cDNA sequence is not closely related to any CA cDNA sequences.
Only very closely related nt sequences having a homology of at least 80-90% would hybridize to each other under stringent conditions. A sequence comparison of the MN cDNA sequence shown in FIG. 1 and a corresponding cDNA of the human carbonic anhydrase II (CA II) showed that there are no stretches of identity between the two sequences that would be long enough to allow for a segment of the CA II cDNA sequence having 50 or more nucleotides to hybridize under stringent hybridization conditions to the MN cDNA or vice versa.
A search for nt sequences related to MN gene in the EMBL Data Library did not reveal any specific homology except for 6 complete and 2 partial Alu-type repeats with homology to Alu sequences ranging from 69.8% to 91% [Jurka and Milosavljevic, J. Mol. Evol. 32: 105-121 (1991)]. Below under the Characterization of the 5' Flanking Region, also a 222 bp sequence proximal to the 5' end of the genomic region is shown to be closely homologous to a region of the HERV-K LTR.
MN Proteins and/or Polypeptides
The phrase "MN proteins and/or polypeptides" (MN proteins/polypeptides) is herein defined to mean proteins and/or polypeptides encoded by an MN gene or fragments thereof. An exemplary and preferred MN protein according to this invention has the deduced amino acid sequence shown in FIG. 1. Preferred MN proteins/polypeptides are those proteins and/or polypeptides that have substantial homology with the MN protein shown in FIG. 1. For example, such substantially homologous MN proteins/polypeptides are those that are reactive with the MN-specific antibodies of this invention, preferably the Mabs M75, MN12, MN9 and MN7 or their equivalents.
A "polypeptide" is a chain of amino acids covalently bound by peptide linkages and is herein considered to be composed of 50 or less amino acids. A "protein" is herein defined to be a polypeptide composed of more than 50 amino acids.
MN proteins exhibit several interesting features: cell membrane localization, cell density dependent expression in HeLa cells, correlation with the tumorigenic phenotype of HeLa x fibroblast somatic cell hybrids, and expression in several human carcinomas among other tissues. As demonstrated herein, for example, in Example 1, MN protein can be found directly in tumor tissue sections but not in general in counterpart normal tissues (exceptions noted infra in Examples 1 and 4-7 as in normal stomach and gallbladder tissues). MN is also expressed sometimes in morphologically normal appearing areas of tissue specimens exhibiting dysplasia and/or malignancy. Taken together, these features suggest a possible involvement of MN in the regulation of cell proliferation, differentiation and/or transformation.
It can be appreciated that a protein or polypeptide produced by a neoplastic cell in vivo could be altered in sequence from that produced by a tumor cell in cell culture or by a transformed cell. Thus, MN proteins and/or polypeptides which have varying amino acid sequences including without limitation, amino acid substitutions, extensions, deletions, truncations and combinations thereof, fall within the scope of this invention. It can also be appreciated that a protein extant within body fluids is subject to degradative processes, such as, proteolytic processes; thus, MN proteins that are significantly truncated and MN polypeptides may be found in body fluids, such as, sera. The phrase "MN antigen" is used herein to encompass MN proteins and/or polypeptides.
It will further be appreciated that the amino acid sequence of MN proteins and polypeptides can be modified by genetic techniques. One or more amino acids can be deleted or substituted. Such amino acid changes may not cause any measurable change in the biological activity of the protein or polypeptide and result in proteins or polypeptides which are within the scope of this invention, as well as, MN muteins.
The MN proteins and polypeptides of this invention can be prepared in a variety of ways according to this invention, for example, recombinantly, synthetically or otherwise biologically, that is, by cleaving longer proteins and polypeptides enzymatically and/or chemically. A preferred method to prepare MN proteins is by a recombinant means. Particularly preferred methods of recombinantly producing MN proteins are described below for the GEX-3X-MN, MN 20-19, MN-Fc and MN-PA proteins.
Recombinant Production of MN Proteins and Polypeptides
A representative method to prepare the MN proteins shown in FIG. 1 or fragments thereof would be to insert the full-length or an appropriate fragment of MN cDNA into an appropriate expression vector as exemplified below. In Zavada et al., WO 93/18152, supra, production of a fusion protein GEX-3X-MN using the partial cDNA clone (described above) in the vector pGEX-3X (Pharmacia) is described. Nonglycosylated GEX-3X-MN (the MN fusion protein MN glutathione S-transferase) from XL1-Blue cells. Herein described is the recombinant production of both a glycosylated MN protein expressed from insect cells and a nonglycosylated MN protein expressed from E. coli using the expression plasmid pEt-22b [Novagen Inc.; Madison, Wis. (USA)].
Baculovirus Expression Systems. Recombinant baculovirus express vectors have been developed for infection into several types of insect cells. For example, recombinant baculoviruses have been developed for among others: Aedes aegypti, Autographa californica, Bombyx mor, Drosphila melanogaster, Reliothis zea, Spodoptera frugiperda, and Trichoplusia ni [PCT Pub. No. WO 89/046699; Wright, Nature, 321: 718 (1986); Fraser et al., In Vitro Cell Dev. Biol., 25: 225 (1989). Methods of introducing exogenous DNA into insect hosts are well-known in the art. DNA transfection and viral infection procedures usually vary with the insect genus to be transformed. See, for example, Autographa [Carstens et al., Virology, 101: 311 (1980)]; Spodoptera [Kang, "Baculovirus Vectors for Expression of Foreign Genes," in: Advances in Virus Research, 35 (1988)]; and Heliothis (virescens) [PCT Pub. No. WO 88/02030].
A wide variety of other host-cloning vector combinations may be usefully employed in cloning the MN DNA isolated as described herein. For example, useful cloning vehicles may include chromosomal, nonchromosomal and synthetic DNA sequences such as various known bacterial plasmids such as pBR322, other E. coli plasmids and their derivatives and wider host range plasmids such as RP4, phage DNA, such as, the numerous derivatives of phage lambda, e.g., NB989 and vectors derived from combinations of plasmids and phage DNAs such as plasmids which have been modified to employ phage DNA expression control sequences.
Useful hosts may be eukaryotic or prokaryotic and include bacterial hosts such as E. coli and other bacterial strains, yeasts and other fungi, animal or plant hosts such as animal or plant cells in culture, insect cells and other hosts. Of course, not all hosts may be equally efficient. The particular selection of host-cloning vehicle combination may be made by those of skill in the art after due consideration of the principles set forth herein without departing from the scope of this invention.
The following are representative examples of genetically engineering MN proteins of this invention. The descriptions are exemplary and not meant to limit the invention in any way.
Expression of MN 20-19 Protein
A representative, recombinantly produced MN protein of this invention is the MN 20-19 protein which, when produced in baculovirus-infected Sf9 cells [Spodoptera frugiderda cells; Clontech; Palo Alto, Calif. (USA)], is glycosylated. The MN 20-19 protein misses the putative signal peptide (aas 1-37) of SEQ. ID. NO.: 6 (FIG. 1), has a methionine (Met) at the N-terminus for expression, and a Leu-Glu-His-His-His-His-His-His [SEQ. ID NO.: 22] added to the C-terminus for purification.
In order to insert the portion of the MN coding sequence for the GEX-3X-MN fusion protein into alternate expression systems, a set of primers for PCR was designed. The primers were constructed to provide restriction sites at each end of the coding sequence, as well as in-frame start and stop codons. The sequences of the primers, indicating restriction enzyme cleavage sites and expression landmarks, are shown below.
The SEQ. ID. NOS.: 17 and 18 primers were used to amplify the MN coding sequence present in the GEX-3X-MN vector using standard PCR techniques. The resulting PCR product (termed MN 20-19) was electrophoresed on a 0.5% agarose/1X TBE gel; the 1.3 kb band was excised; and the DNA recovered using the Gene Clean II kit according to the manufacturer's instructions [Bio101; Lajolla, Calif. (USA)].
MN 20-19 and plasmid pET-22b were cleaved with the restriction enzymes NdeI and XhoI, phenol-chloroform extracted, and the appropriate bands recovered by agarose gel electrophoresis as above. The isolated fragments were ethanol co-precipitated at a vector:insert ratio of 1:4. After resuspension, the fragments were ligated using T4 DNA ligase. The resulting product was used to transform competent Novablue E. coli cells [Novagen, Inc.]. Plasmid mini-preps [Magic Minipreps; Promega] from the resultant ampicillin resistant colonies were screened for the presence of the correct insert by restriction mapping. Insertion of the gene fragment into the pET-22b plasmid using the NdeI and XhoI sites added a 6-histidine tail to the protein that could be used for affinity isolation.
To prepare MN 20-19 for insertion into the baculovirus expression system, the MN 20-19 gene fragment was excised from pET-22b using the restriction endonucleases XbaI and PvuI. The baculovirus shuttle vector pBacPAK8 [Clontech] was cleaved with XbaI and PacI. The desired fragments (1.3 kb for MN 20-19 and 5.5 kb for pBacPAK8) were isolated by agarose gel electrophoresis, recovered using Gene Clean II, and co-precipitated at an insert:vector ratio of 2.4:1.
After ligation with T4 DNA ligase, the DNA was used to transform competent NM522 E. coli cells (Stratagene). Plasmid mini-preps from resultant ampicillin resistant colonies were screened for the presence of the correct insert by restriction mapping. Plasmid DNA from an appropriate colony and linearized BacPAK6 baculovirus DNA [Clontech] were used to transform Sf9 cells by standard techniques. Recombination produced BacPAK viruses carrying the MN 20-19 sequence. Those viruses were plated onto Sf9 cells and overlaid with agar.
Plaques were picked and plated onto Sf9 cells. The conditioned media and cells were collected. A small aliquot of the conditioned media was set aside for testing. The cells were extracted with PBS with 1% Triton X100.
The conditioned media and the cell extracts were dot blotted onto nitrocellulose paper. The blot was blocked with 5% non-fat dried milk in PBS. Mab M75 were used to detect the MN 20-19 protein in the dot blots. A rabbit anti-mouse Ig-HRP was used to detect bound Mab M75. The blots were developed with TMB/H.sub.2 O.sub.2 with a membrane enhancer [KPL; Gaithersburg, Md. (USA)]. Two clones producing the strongest reaction on the dot blots were selected for expansion. One was used to produce MN 20-19 protein in High Five cells [Invitrogen Corp., San Diego, Calif. (USA); BTI-TN-5BI-4; derived from Trichoplusia ni egg cell homogenate]. MN 20-19 protein was purified from the conditioned media from the virus infected High Five cells.
The MN 20-19 protein was purified from the conditioned media by immunoaffinity chromatography. 6.5 mg of Mab M75 was coupled to 1 g of Tresyl activated Toyopearl.TM. [Tosoh, Japan (#14471)]. Approximately 150 ml of the conditioned media was run through the M75-Toyopearl column. The column was washed with PBS, and the MN 20-19 protein was eluted with 1.5 M MgCl. The eluted protein was then dialyzed against PBS.
Synthetic and Biologic Production of MN Proteins and Polypeptides
MN proteins and polypeptides of this invention may be prepared not only by recombinant means but also by synthetic and by other biologic means. Synthetic formation of the polypeptide or protein requires chemically synthesizing the desired chain of amino acids by methods well known in the art. Exemplary of other biologic means to prepare the desired polypeptide or protein is to subject to selective proteolysis a longer MN polypeptide or protein containing the desired amino acid sequence; for example, the longer polypeptide or protein can be split with chemical reagents or with enzymes.
Chemical synthesis of a peptide is conventional in the art and can be accomplished, for example, by the Merrifield solid phase synthesis technique [Merrifield, J., Am. Chem. Soc., 85: 2149-2154 (1963); Kent et al., Synthetic Peptides in Biology and Medicine, 29 f.f. eds. Alitalo et al., (Elsevier Science Publishers 1985); and Haug, J. D., American Biotechnology Laboratory, 5(1): 40-47 (January/February 1987)].
Techniques of chemical peptide synthesis include using automatic peptide synthesizers employing commercially available protected amino acids, for example, Biosearch [San Rafael, Calif. (USA)] Models 9500 and 9600; Applied Biosystems, Inc. [Foster City, Calif. (USA)] Model 430; Milligen [a division of Millipore Corp.; Bedford, Mass. (USA)] Model 9050; and Du Pont's RAMP (Rapid Automated Multiple Peptide Synthesis) [Du Pont Compass, Wilmington, Del. (USA)].
Regulation of MN Expression and MN Promoter
MN appears to be a novel regulatory protein that is directly involved in the control of cell proliferation and in cellular transformation. In HeLa cells, the expression of MN is positively regulated by cell density. Its level is increased by persistent infection with LCMV. In hybrid cells between HeLa and normal fibroblasts, MN expression correlates with tumorigenicity. The fact that MN is not present in nontumorigenic hybrid cells (CGL1), but is expressed in a tumorigenic segregant lacking chromosome 11, indicates that MN is negatively regulated by a putative suppressor in chromosome 11.
Evidence supporting the regulatory role of MN protein was found in the generation of stable transfectants of NIH 3T3 cells that constitutively express MN protein. As a consequence of MN expression, the NIH 3T3 cells acquired features associated with a transformed phenotype: altered morphology, increased saturation density, proliferative advantage in serum-reduced media, enhanced DNA synthesis and capacity for anchorage-independent growth. Further, flow cytometric analyses of asynchronous cell populations indicated that the expression of MN protein leads to accelerated progression of cells through G1 phase, reduction of cell size and the loss of capacity for growth arrest under inappropriate conditions. Also, MN expressing cells display a decreased sensitivity to the DNA damaging drug mitomycin C.
Nontumorigenic human cells, CGL1 cells, were also transfected with the full-length MN cDNA. The same pSG5C-MN construct in combination with pSV2neo plasmid as used to transfect the NIH 3T3 cells was used. Out of 15 MN-positive clones (tested by SP-RIA and Western blotting), 3 were chosen for further analysis. Two MN-negative clones isolated from CGL1 cells transfected with empty plasmid were added as controls. Initial analysis indicates that the morphology and growth habits of MN-transfected CGL1 cells are not changed dramatically, but their proliferation rate and plating efficiency is increased.
MN Promoter--Sense/Antisense Constructs
When the promoter region from the MN genomic clone, isolated as described above, was linked to MN cDNA and transfected into CGL1 hybrid cells, expression of MN protein was detectable immediately after selection. However, then it gradually ceased, indicating thus an action of a feedback regulator. The putative regulatory element appeared to be acting via the MN promoter, because when the full-length cDNA (not containing the promoter) was used for transfection, no similar effect was observed.
An "antisense" MN cDNA/MN promoter construct was used to transfect CGL3 cells. The effect was the opposite of that of the CGL1 cells transfected with the "sense" construct. Whereas the transfected CGL1 cells formed colonies several times larger than the control CGL1, the transfected CGL3 cells formed colonies much smaller than the control CGL3 cells. The same result was obtained by antisense MN cDNA transfection in SiHa and HeLa cells.
For those experiments, the part of the promoter region that was linked to the MN cDNA through a BamHI site was derived from a NcoI-BamHI fragment of the MN genomic clone [Bd3] and represents a region a few hundred bp upstream from the transcription initiation site. After the ligation, the joint DNA was inserted into a PBK-CMV expression vector [Stratagene]. The required orientation of the inserted sequence was ensured by directional cloning and subsequently verified by restriction analysis. The tranfection procedure was the same as used in transfecting the NIH 3T3 cells, but co-transfection with the pSV2neo plasmid was not necessary since the neo selection marker was already included in the pBK-CMV vector.
After two weeks of selection in a medium containing G418, remarkable differences between the numbers and sizes of the colonies grown were evident as noted above. Immediately following the selection and cloning, the MN-transfected CGL1 and CGL3 cells were tested by SP-RIA for expression and repression of MN, respectively. The isolated transfected CGL1 clones were MN positive (although the level was lower than obtained with the full-length cDNA), whereas MN protein was almost absent from the transfected CGL3 clones. However, in subsequent passages, the expression of MN in transfected CGL1 cells started to cease, and was then blocked perhaps evidencing a control feedback mechanism.
As a result of the very much lowered proliferation of the transfected CGL3 cells, it was difficult to expand the majority of cloned cells (according to SP-RIA, those with the lowest levels of MN), and they were lost during passaging. However, some clones overcame that problem and again expressed MN. It is possible that once those cells reached a higher quantity, that the level of endogenously produced MN mRNA increased over the amount of ectopically expressed antisense mRNA.
Nucleic Acid Probes and Test Kits
Nucleic acid probes of this invention are those comprising sequences that are complementary or substantially complementary to the MN cDNA sequence shown in FIG. 1 or to other MN gene sequences, such as, the complete genomic sequence of FIGS. 2A-F [SEQ. ID. NO.: 5] and the putative promoter sequence [SEQ. ID. NO.: 27 of FIG. 6]. The phrase "substantially complementary" is defined herein to have the meaning as it is well understood in the art and, thus, used in the context of standard hybridization conditions. The stringency of hybridization conditions can be adjusted to control the precision of complementarity. Two nucleic acids are, for example, substantially complementary to each other, if they hybridize to each other under stringent hybridization conditions.
Stringent hybridization conditions are considered herein to conform to standard hybridization conditions understood in the art to be stringent. For example, it is generally understood that stringent conditions encompass relatively low salt and/or high temperature conditions, such as provided by 0.02 M to 0.15 M NaCl at temperatures of 50.degree. C. to 70.degree. C. Less stringent conditions, such as, 0.15 M to 0.9 M salt at temperatures ranging from 20.degree. C. to 55.degree. C. can be made more stringent by adding increasing amounts of formamide, which serves to destabilize hybrid duplexes as does increased temperature.
Exemplary stringent hybridization conditions are described in Sambrook et al., Molecular Cloning: A Laboratory Manual, pages 1.91 and 9.47-9.51 (Second Edition, Cold Spring Harbor Laboratory Press; Cold Spring Harbor, N.Y.; 1989); Maniatis et al., Molecular Cloning: A Laboratory Manual, pages 387-389 (Cold Spring Harbor Laboratory; Cold Spring Harbor, N.Y.; 1982); Tsuchiya et al., Oral Surgery, Oral Medicine, Oral Pathology, 71(6): 721-725 (June 1991).
Preferred nucleic acid probes of this invention are fragments of the isolated nucleic acid sequences that encode MN proteins or polypeptides according to this invention. Preferably those probes are composed of at least twenty-nine nucleotides, more preferably, fifty nucleotides.
Nucleic acid probes of this invention need not hybridize to a coding region of MN. For example, nucleic acid probes of this invention may hybridize partially or wholly to a non-coding region of the genomic sequence shown in FIGS. 2A-F [SEQ. ID. NO.: 5]. Conventional technology can be used to determine whether fragments of SEQ. ID. NO.: 5 or related nucleic acids are useful to identify MN nucleic acid sequences. [See, for example, Benton and Davis, supra and Fuscoe et al., supra.]
Areas of homology of the MN nt sequence to other non-MN nt sequences are indicated above. In general, nucleotide sequences that are not in the Alu or LTR-like regions, of preferably 29 bases or more, or still more preferably of 50 bases or more, can be routinely tested and screened and found to hybridize under stringent conditions to only MN nucleotide sequences. Further, not all homologies within the Alu-like MN genomic sequences are so close to Alu repeats as to give a hybridization signal under stringent hybridization conditions. The percent of homology between MN Alu-like regions and a standard Alu-J sequence are indicated as follows:
Nucleic acid probes of this invention can be used to detect MN DNA and/or RNA, and thus can be used to test for the presence or absence of MN genes, and amplification(s), mutation(s) or genetic rearrangements of MN genes in the cells of a patient. For example, overexpression of an MN gene may be detected by Northern blotting and RNase protection analysis using probes of this invention. Gene alterations, as amplifications, translocations, inversions, and deletions among others, can be detected by using probes of this invention for in situ hybridization to chromosomes from a patient's cells, whether in metaphase spreads or interphase nuclei. Southern blotting could also be used with the probes of this invention to detect amplifications or deletions of MN genes. Restriction Fragment Length Polymorphism (RFLP) analysis using said probes is a preferred method of detecting gene alterations, mutations and deletions. Said probes can also be used to identify MN proteins and/or polypeptides as well as homologs or near homologs thereto by their hybridization to various mRNAs transcribed from MN genes in different tissues.
Probes of this invention thus can be useful diagnostically/prognostically. Said probes can be embodied in test kits, preferably with appropriate means to enable said probes when hybridized to an appropriate MN gene or MN mRNA target to be visualized. Such samples include tissue specimens including smears, body fluids and tissue and cell extracts.
PCR Assays
To detect relatively large genetic rearrangements, hybridization tests can be used. To detect relatively small genetic rearrangements, as, for example, small deletions or amplifications, or point mutations, PCR would preferably be used. [U.S. Pat. Nos. 4,800,159; 4,683,195; 4,683,202; and Chapter 14 of Sambrook et al., Molecular Cloning: A Laboratory Manual, supra]
An exemplary assay would use cellular DNA from normal and cancerous cells, which DNA would be isolated and amplified employing appropriate PCR primers. The PCR products would be compared, preferably initially, on a sizing gel to detect size changes indicative of certain genetic rearrangements. If no differences in sizes are noted, further comparisons can be made, preferably using, for example, PCR-single-strand conformation polymorphism (PCR-SSCP) assay or a denaturing gradient gel electrophoretic assay. [See, for example, Hayashi, K. in PCR Methods and Applications, 1: 34-38 (1991); and Meyers et al., Methods in Enzymology, 155: 501 (1987).]
Assays
Assays according to this invention are provided to detect and/or quantitate MN antigen or MN-specific antibodies in vertebrate samples, preferably mammalian samples, more preferably human samples. Such samples include tissue specimens, body fluids, tissue extracts, cells, cell lysates and cell extracts, among other samples. MN antigen may be detected by immunoassay, immunohistochemical staining, immunoelectron and scanning microscopy using immunogold among other techniques.
Preferred tissue specimens to assay by immunohistochemical staining include cell smears, histological sections from biopsied tissues or organs, and imprint preparations among other tissue samples. Such tissue specimens can be variously maintained, for example, they can be fresh, frozen, or formalin-, alcohol- or acetone- or otherwise fixed and/or paraffin-embedded and deparaffinized. Biopsied tissue samples can be, for example, those samples removed by aspiration, bite, brush, cone, chorionic villus, endoscopic, excisional, incisional, needle, percutaneous punch, and surface biopsies, among other biopsy techniques.
Preferred cervical tissue specimens include cervical smears, conization specimens, histologic sections from hysterectomy specimens or other biopsied cervical tissue samples. Preferred means of obtaining cervical smears include routine swab, scraping or cytobrush techniques, among other means. More preferred are cytobrush or swab techniques. Preferably, cell smears are made on microscope slides, fixed, for example, with 55% EtOH or an alcohol based spray fixative and air-dried.
Papanicolaou-stained cervical smears (Pap smears) can be screened by the methods of this invention, for example, for retrospective studies. Preferably, Pap smears would be decolorized and re-stained with labeled antibodies against MN antigen. Also archival specimens, for example, matched smears and biopsy and/or tumor specimens, can be used for retrospective studies. Prospective studies can also be done with matched specimens from patients that have a higher than normal risk of exhibiting abnormal cervical cytopathology.
Preferred samples in which to assay MN antigen by, for example, Western blotting or radioimmunoassay, are tissue and/or cell extracts. However, MN antigen, particularly in a soluble form, as the extracellular domain, can be detected in body fluids, which can include among other fluids: blood, serum, plasma, semen, breast exudate, gastric secretions, fecal suspensions, bile, saliva, tears, sputum, mucous, urine, lymph, cytosols, ascites, pleural effusions, amniotic fluid, bladder washes, bronchioalveolar lavages and cerebrospinal fluid. It is preferred that the MN antigen be concentrated from a larger volume of body fluid before testing. Preferred body fluids to assay would depend on the type of cancer for which one was testing, but in general preferred body fluids would be urine, serum, mucous, gastric secretions, bile, breast exudate, pleural effusions and ascites.
Diagnostic nucleic acid can be labelled, directly or indirectly, by methods known in the art, and can be used in conventional Southern or Northern hybridization assays. Such assays can be employed in identifying transformants or for in vitro diagnosis, such as to detect MN mRNA in tissues as a measure of oncogenic activity. The presence of MN mRNA or precursors thereto for most tissues being indicative of oncogenic activity, whereas the absence or a reduced level of MN mRNA in stomach, gallbladder and other certain tissues of the alimentary tract in comparison to the levels of mRNA found in the counterpart normal tissues is considered indicative of oncogenic activity. DNA which encodes MN proteins can be obtained by chemical synthesis, by screening reverse transcripts of mRNA from placental or other cells, or by screening genomic libraries from eukaryotic cells, among other methods.
MN-specific antibodies can be bound by serologically active MN proteins/polypeptides in samples of such body fluids as blood, plasma, serum, lymph, mucous, tears, urine, spinal fluid and saliva; however, such antibodies are found most usually in blood, plasma and serum, preferably in serum. Correlation of the results from the assays to detect and/or quantitate MN antigen and MN-specific antibodies reactive therewith, provides a preferred profile of the disease condition of a patient.
The assays of this invention are both diagnostic and/or prognostic, i.e., diagnostic/prognostic. The term "diagnostic/ prognostic" is herein defined to encompass the following processes either individually or cumulatively depending upon the clinical context: determining the presence of disease, determining the nature of a disease, distinguishing one disease from another, forecasting as to the probable outcome of a disease state, determining the prospect as to recovery from a disease as indicated by the nature and symptoms of a case, monitoring the disease status of a patient, monitoring a patient for recurrence of disease, and/or determining the preferred therapeutic regimen for a patient. The diagnostic/prognostic methods of this invention are useful, for example, for screening populations for the presence of neoplastic or pre-neoplastic disease, determining the risk of developing neoplastic disease, diagnosing the presence of neoplastic and/or pre-neoplastic disease, monitoring the disease status of patients with neoplastic disease, and/or determining the prognosis for the course of neoplastic disease. For example, it appears that the intensity of the immunostaining with MN-specific antibodies may correlate with the severity of dysplasia present in samples tested.
The present invention is useful for screening for the presence of a wide variety of neoplastic diseases as indicated above. The invention provides methods and compositions for evaluating the probability of the presence of malignant or pre-malignant cells, for example, in a group of cells freshly removed from a host. Such an assay can be used to detect tumors, quantitate their growth, and help in the diagnosis and prognosis of disease. The assays can also be used to detect the presence of cancer metastasis, as well as confirm the absence or removal of all tumor tissue following surgery, cancer chemotherapy and/or radiation therapy. It can further be used to monitor cancer chemotherapy and tumor reappearance.
The presence of MN antigen or antibodies can be detected and/or quantitated using a number of well-defined diagnostic assays. Those in the art can adapt any of the conventional immunoassay formats to detect and/or quantitate MN antigen and/or antibodies.
Many formats for detection of MN antigen and MN-specific antibodies are, of course available. Those can be Western blots, ELISAs, RIAs, competitive EIA or dual antibody sandwich assays, immunohistochemical staining, among other assays all commonly used in the diagnostic industry. In such immunoassays, the interpretation of the results is based on the assumption that the antibody or antibody combination will not cross-react with other proteins and protein fragments present in the sample that are unrelated to MN.
Representative of one type of ELISA test for MN antigen is a format wherein a microtiter plate is coated with antibodies made to MN proteins/polypeptides or antibodies made to whole cells expressing MN proteins, and to this is added a patient sample, for example, a tissue or cell extract. After a period of incubation permitting any antigen to bind to the antibodies, the plate is washed and another set of anti-MN antibodies which are linked to an enzyme is added, incubated to allow reaction to take place, and the plate is then rewashed. Thereafter, enzyme substrate is added to the microtiter plate and incubated for a period of time to allow the enzyme to work on the substrate, and the adsorbance of the final preparation is measured. A large change in absorbance indicates a positive result.
It is also apparent to one skilled in the art of immunoassays that MN proteins and/or polypeptides can be used to detect and/or quantitate the presence of MN antigen in the body fluids, tissues and/or cells of patients. In one such embodiment, a competition immunoassay is used, wherein the MN protein/polypeptide is labeled and a body fluid is added to compete the binding of the labeled MN protein/polypeptide to antibodies specific to MN protein/polypeptide.
In another embodiment, an immunometric assay may be used wherein a labeled antibody made to a MN protein or polypeptide is used. In such an assay, the amount of labeled antibody which complexes with the antigen-bound antibody is directly proportional to the amount of MN antigen in the sample.
A representative assay to detect MN-specific antibodies is a competition assay in which labeled MN protein/polypeptide is precipitated by antibodies in a sample, for example, in combination with monoclonal antibodies recognizing MN proteins/polypeptides. One skilled in the art could adapt any of the conventional immunoassay formats to detect and/or quantitate MN-specific antibodies. Detection of the binding of said antibodies to said MN protein/polypeptide could be by many ways known to those in the art, e.g., in humans with the use of anti-human labeled IgG.
An exemplary immunoassay method of this invention to detect and/or quantitate MN antigen in a vertebrate sample comprises the steps of:
a) incubating said vertebrate sample with one or more sets of antibodies (an antibody or antibodies) that bind to MN antigen wherein one set is labeled or otherwise detectable;
b) examining the incubated sample for the presence of immune complexes comprising MN antigen and said antibodies.
Another exemplary immunoassay method according to this invention is that wherein a competition immunoassay is used to detect and/or quantitate MN antigen in a vertebrate sample and wherein said method comprises the steps of:
a) incubating a vertebrate sample with one or more sets of MN-specific antibodies and a certain amount of a labeled or otherwise detectable MN protein/polypeptide wherein said MN protein/ polypeptide competes for binding to said antibodies with MN antigen present in the sample;
b) examining the incubated sample to determine the amount of labeled/detectable MN protein/polypeptide bound to said antibodies; and
c) determining from the results of the examination in step b) whether MN antigen is present in said sample and/or the amount of MN antigen present in said sample.
Once antibodies (including biologically active antibody fragments) having suitable specificity have been prepared, a wide variety of immunological assay methods are available for determining the formation of specific antibody-antigen complexes. Numerous competitive and non-competitive protein binding assays have been described in the scientific and patent literature, and a large number of such assays are commercially available. Exemplary immunoassays which are suitable for detecting a serum antigen include those described in U.S. Pat. Nos. 3,984,533; 3,996,345; 4,034,074; and 4,098,876.
Antibodies employed in assays may be labeled or unlabeled. Unlabeled antibodies may be employed in agglutination; labeled antibodies may be employed in a wide variety of assays, employing a wide variety of labels.
Suitable detection means include the use of labels such as radionuclides, enzymes, coenzymes, fluorescers, chemiluminescers, chromogens, enzyme substrates or co-factors, enzyme inhibitors, free radicals, particles, dyes and the like. Such labeled reagents may be used in a variety of well known assays, such as radioimmunoassays, enzyme immunoassays, e.g., ELISA, fluorescent immunoassays, and the like. See for example, U.S. Pat. Nos. 3,766,162; 3,791,932; 3,817,837; and 4,233,402.
Immunoassay Test Kits
The above outlined assays can be embodied in test kits to detect and/or quantitate MN antigen and/or MN-specific antibodies (including biologically active antibody fragments). Kits to detect and/or quantitate MN antigen can comprise MN protein(s)/polypeptides(s) and/or MN-specific antibodies, polyclonal and/or monoclonal. Such diagnostic/prognostic test kits can comprise one or more sets of antibodies, polyclonal and/or monoclonal, for a sandwich format wherein antibodies recognize epitopes on the MN antigen, and one set is appropriately labeled or is otherwise detectable.
Test kits for an assay format wherein there is competition between a labeled (or otherwise detectable) MN protein/polypeptide and MN antigen in the sample, for binding to an antibody, can comprise the combination of the labeled protein/polypeptide and the antibody in amounts which provide for optimum sensitivity and accuracy.
Test kits for MN-specific antibodies preferably comprise labeled/detectable MN proteins(s) and/or polypeptides(s), and may comprise other components as necessary, such as, controls, buffers, diluents and detergents. Such test kits can have other appropriate formats for conventional assays.
A kit for use in an enzyme-immunoassay typically includes an enzyme-labelled reagent and a substrate for the enzyme. The enzyme can, for example, bind either an MN-specific antibody of this invention or to an antibody to such an MN-specific antibody.
Preparation of MN-Specific Antibodies
The term "antibodies" is defined herein to include not only whole antibodies but also biologically active fragments of antibodies, preferably fragments containing the antigen binding regions. Further included in the definition of antibodies are bispecific antibodies that are specific for MN protein and to another tissue-specific antigen.
Antibodies of the invention may be prepared by conventional methodology and/or by genetic engineering. Antibody fragments may be genetically engineered, preferably from the variable regions of the light and/or heavy chains (V.sub.H and V.sub.L), including the hypervariable regions, and still more preferably from both the V.sub.H and V.sub.L regions. For example, the term "antibodies" as used herein comprehends polyclonal and monoclonal antibodies and biologically active fragments thereof including among other possibilities "univalent" antibodies [Glennie et al., Nature, 295: 712 (1982)); Fab proteins including Fab' and F(ab').sub.2 fragments whether covalently or non-covalently aggregated; light or heavy chains alone, preferably variable heavy and light chain regions (V.sub.H and V.sub.L regions), and more preferably including the hypervariable regions [otherwise known as the complementarity determining regions (CDRs) of said V.sub.H and V.sub.L regions]; F.sub.c proteins; "hybrid" antibodies capable of binding more than one antigen; constant-variable region chimeras; "composite" immunoglobulins with heavy and light chains of different origins; "altered" antibodies with improved specificity and other characteristics as prepared by standard recombinant techniques and also by oligonucleotide-directed mutagenesis techniques [Dalbadie-McFarland et al., PNAS (USA), 79: 6409 (1982)].
Bispecific Antibodies. Bispecific antibodies can be produced by chemically coupling two antibodies of the desired specificity. Bispecific MAbs can preferably be developed by somatic hybridization of 2 hybridomas. Bispecific MAbs for targeting MN protein and another antigen can be produced by fusing a hybridoma that produces MN-specific MAbs with a hybridoma producing MAbs specific to another antigen. For example, a cell (a quadroma), formed by fusion of a hybridoma producing a MN-specific MAb and a hybridoma producing an anti-cytotoxic cell antibody, will produce hybrid antibody having specificity of the parent antibodies. [See, e.g., Immunol. Rev. (1979); Cold Spring Harbor Symposium Quant. Biol., 41: 793 (1977); van Dijk et al., Int. J. Cancer, 43: 344-349 (1989).] Thus, a hybridoma producing a MN-specific MAb can be fused with a hybridoma producing, for example, an anti-T3 antibody to yield a cell line which produces a MN/T3 bispecific antibody which can target cytotoxic T cells to MN-expressing tumor cells.
It may be preferred for therapeutic and/or imaging uses that the antibodies be biologically active antibody fragments, preferably genetically engineered fragments, more preferably genetically engineered fragments from the V.sub.H and/or V.sub.L regions, and still more preferably comprising the hypervariable regions thereof. However, for some therapeutic uses bispecific antibodies targeting MN protein and cytotoxic cells would be preferred.
There are conventional techniques for making polyclonal and monoclonal antibodies well-known in the immunoassay art. Immunogens to prepare MN-specific antibodies include MN proteins and/or polypeptides, preferably purified, and MX-infected tumor line cells, for example, MX-infected HeLa cells, among other immunogens.
Anti-peptide antibodies are also made by conventional methods in the art as described in European Patent Publication No. 44,710 (published Jan. 27, 1982). Briefly, such anti-peptide antibodies are prepared by selecting a peptide from an MN amino acid sequence as from FIG. 1, chemically synthesizing it, conjugating it to an appropriate immunogenic protein and injecting it into an appropriate animal, usually a rabbit or a mouse; then, either polyclonal or monoclonal antibodies are made, the latter by a Kohler-Milstein procedure, for example.
Besides conventional hybridoma technology, newer technologies can be used to produce antibodies according to this invention. For example, the use of the PCR to clone and express antibody V-genes and phage display technology to select antibody genes encoding fragments with binding activities has resulted in the isolation of antibody fragments from repertoires of PCR amplified V-genes using immunized mice or humans. [Marks et al., BioTechnology, 10: 779 (July 1992) for references; Chiang et al., BioTechniques, 7(4): 360 (1989); Ward et al., Nature, 341: 544 (Oct. 12, 1989); Marks et al., J. Mol. Biol., 222: 581 (1991); Clackson et al., Nature, 352: (Aug. 15, 1991); and Mullinax et al., PNAS (USA), 87: 8095 (October 1990).]
Descriptions of preparing antibodies, which term is herein defined to include biologically active antibody fragments, by recombinant techniques can be found in U.S. Pat. No. 4,816,567 (issued Mar. 28, 1989); European Patent Application Publication Number (EP) 338,745 (published Oct. 25, 1989); EP 368,684 (published Jun. 16, 1990); EP 239,400 (published Sep. 30, 1987); WO 90/14424 (published Nov. 29, 1990); WO 90/14430 (published May 16, 1990); Huse et al., Science, 246: 1275 (Dec. 8, 1989); Marks et al., BioTechnology, 10: 779 (July 1992); La Sastry et al., PNAS (USA), 86: 5728 (August 1989); Chiang et al., BioTechniques, 7(40): 360 (1989); Orlandi et al., PNAS (USA), 86: 3833 (May 1989); Ward et al. Nature, 341: 544 (Oct. 12, 1989); Marks et al., J. Mol. Biol., 222: 581 (1991); and Hoogenboom et al., Nucleic Acids Res., 19(15): 4133 (1991).
Representative Mabs
Monoclonal antibodies for use in the assays of this invention may be obtained by methods well known in the art for example, Galfre and Milstein, "Preparation of Monoclonal Antibodies: Strategies and Procedures," in Methods in Enzymology: Immunochemical Techniques, 73: 1-46 [Langone and Vanatis (eds); Academic Press (1981)]; and in the classic reference, Milstein and Kohler, Nature, 256: 495-497 (1975).]
Although representative hybridomas of this invention are formed by the fusion of murine cell lines, human/human hybridomas [Olsson et al., PNAS (USA), 77: 5429 (1980)] and human/murine hybridomas [Schlom et al., PNAS (USA), 77: 6841 (1980); Shearman et al. J. Immunol., 146: 928-935 (1991); and Gorman et al., PNAS (USA), 88: 4181-4185 (1991)] can also be prepared among other possiblities. Such humanized monoclonal antibodies would be preferred monoclonal antibodies for therapeutic and imaging uses.
Monoclonal antibodies specific for this invention can be prepared by immunizing appropriate mammals, preferably rodents, more preferably rabbits or mice, with an appropriate immunogen, for example, MaTu-infected HeLa cells, MN fusion proteins, or MN proteins/polypeptides attached to a carrier protein if necessary. Exemplary methods of producing antibodies of this invention are described below.
The monoclonal antibodies useful according to this invention to identify MN proteins/polypeptides can be labeled in any conventional manner, for example, with enzymes such as horseradish peroxidase (HRP), fluorescent compounds, or with radioactive isotopes such as, .sup.125 I, among other labels. A preferred label, according to this invention is .sup.125 I, and a preferred method of labeling the antibodies is by using chloramine-T [Hunter, W. M., "Radioimmunoassay," In: Handbook of Experimental Immunology, pp. 14.1-14.40 (D. W. Weir ed.; Blackwell, Oxford/London/Edinburgh/Melbourne; 1978)].
Representative mabs of this invention include Mabs M75, MN9, MN12 and MN7 described below. Monoclonal antibodies of this invention serve to identify MN proteins/polypeptides in various laboratory diagnostic tests, for example, in tumor cell cultures or in clinical samples.
Mabs Prepared Against HeLa Cells
MAb M75. Monoclonal antibody M75 (MAb M75) is produced by mouse lymphocytic hybridoma VU-M75, which was initially deposited in the Collection of Hybridomas at the Institute of Virology, Slovak Academy of Sciences (Bratislava, Czechoslovakia) and was deposited under ATCC Designation HB 11128 on Sep. 17, 1992 at the American Type Culture Collection (ATCC) in Rockville, Md. (USA). The production of hybridoma VU-M75 is described in Zavada et al., WO 93/18152.
Mab M75 recognizes both the nonglycosylated GEX-3X-MN fusion protein and native MN protein as expressed in CGL3 cells equally well. Mab M75 was shown by epitope mapping to be reactive with the epitope represented by the amino acid sequence from AA 62 to AA 67 [SEQ. ID. NO.: 10] of the MN protein shown in FIG. 1.
Mabs Prepared Against Fusion Protein GEX-3X-MN
Monoclonal antibodies of this invention were also prepared against the MN glutathione S-transferase fusion protein (GEX-3X-MN). BALB/C mice were immunized intraperitoneally according to standard procedures with the GEX-3X-MN fusion protein in Freund's adjuvant. Spleen cells of the mice were fused with SP/20 myeloma cells [Milstein and Kohler, supra].
Tissue culture media from the hybridomas were screened against CGL3 and CGL1 membrane extracts in an ELISA employing HRP labelled-rabbit anti-mouse. The membrane extracts were coated onto microtiter plates. Selected were antibodies reacted with the CGL3 membrane extract. Selected hybridomas were cloned twice by limiting dilution.
The mabs prepared by the just described method were characterized by Western blots of the GEX-3X-MN fusion protein, and with membrane extracts from the CGL1 and CGL3 cells. Representative of the mabs prepared are Mabs MN9, MN12 and MN7.
Mab MN9. Monoclonal antibody MN9 (Mab MN9) reacts to the same epitope as Mab M75, represented by the sequence from aa 62 to aa 67 [SEQ. ID. NO.: 10] of the FIG. 1 MN protein. As Mab M75, Mab MN9 recognizes both the GEX-3X-MN fusion protein and native MN protein equally well.
Mabs corresponding to Mab MN9 can be prepared reproducibly by screening a series of mabs prepared against an MN protein/polypeptide, such as, the GEX-3X-MN fusion protein, against the peptide representing the epitope for Mabs M75 and MN9, that is, SEQ. ID. NO.: 10. Alternatively, the Novatope system [Novagen] or competition with the deposited Mab M75 could be used to select mabs comparable to Mabs M75 and MN9.
Mab MN12. Monoclonal antibody MN12 (Mab MN12) is produced by the mouse lymphocytic hybridoma MN 12.2.2 which was deposited under ATCC Designation HB 11647 on Jun. 9, 1994 at the American Type Culture Collection (ATCC) at 12301 Parklawn Drive, Rockville, Md. 20852 (USA). Antibodies corresponding to Mab MN12 can also be made, analogously to the method outlined above for Mab MN9, by screening a series of antibodies prepared against an MN protein/polypeptide, against the peptide representing the epitope for Mab MN12. That peptide is aa 55-aa 60 of FIG. 1 [SEQ. ID. NO.: 11]. The Novatope system could also be used to find antibodies specific for said epitope.
Mab MN7. Monoclonal antibody MN7 (Mab MN7) was selected from mabs prepared against nonglycosylated GEX-3X-MN as described above. It recognizes the epitope on MN represented by the amino acid sequence from aa 127 to aa 147 [SEQ. ID. NO.: 12] of the FIG. 1 MN protein. Analogously to methods described above for Mabs MN9 and MN12, mabs corresponding to Mab MN7 can be prepared by selecting mabs prepared against an MN protein/polypeptide that are reactive with the peptide having SEQ. ID. NO.: 12, or by the stated alternative means.
Epitope Mapping
Epitope mapping was performed by the Novatope system, a kit for which is commercially available from Novagen, Inc. [See, for analogous example, Li et al., Nature, 363: 85-88 (6 May 1993).] In brief, the MN cDNA was cut into overlapping short fragments of approximately 60 base pairs. The fragments were expressed in E. coli, and the E. coli colonies were transferred onto nitrocellulose paper, lysed and probed with the mab of interest. The MN cDNA of clones reactive with the mab of interest was sequenced, and the epitopes of the mabs were deduced from the overlapping polypeptides found to be reactive with each mab.
Therapeutic Use of MN-Specific Antibodies
The MN-specific antibodies of this invention, monoclonal and/or polyclonal, preferably monoclonal, and as outlined above, may be used therapeutically in the treatment of neoplastic and/or pre-neoplastic disease, either alone or in combination with chemotherapeutic drugs or toxic agents, such as ricin A. Further preferred for therapeutic use would be biologically active antibody fragments as described herein. Also preferred MN-specific antibodies for such therapeutic uses would be humanized monoclonal antibodies and/or bispecific antibodies.
MN-specific antibodies can be administered in a therapeutically effective amount, preferably dispersed in a physiologically acceptable, nontoxic liquid vehicle, to patients afflicted with preneoplastic/neoplastic disease. The MN-specific antibody can be given alone or as a carrier of an anti-tumor drug. Among the various antiproliferative, antineoplastic or cytotoxic agents that may be linked to the MN-specific antibodies are antimetabolites, such as the antifolate, methotrexate, or the purine or pyrimidine analogs mercaptopurine and fluorouracil. Others include antibiotics, lectins such as ricin and abrin, toxins such as the subunit of diphtheria toxin, radionuclides such as .sup.212 Astatine and .sup.131 Iodine, radiosensitizers such as misanidazole or neutron sensitizers such as boron containing organics. Such agents may be attached to the antibody by conventional techniques such as glutaraldehyde cross-linking.
MN-specific antibodies can be used to target cytoxic cells (e.g. human T cells, monocytes or NK cells). Cytotoxic cells can be attached to MN-expressing tumor cells through Fc receptors on the cytotoxic cells, which bind the Fc portion of a MN-specific antibody, or via a bridging antibody of dual specificity, that is, a bispecific antibody specific for MN protein and for the cytotoxic cell.
The cytotoxic cell can be targeted by allowing the bispecific antibody to bind the cell. After targeting, the cells can be administered to the patient. Therapy with targeted cells can be used as an adjunct to surgical therapy, radiation therapy, or chemotherapy.
Imaging Use of Antibodies
Further, the MN-specific antibodies of this invention when linked to an imaging agent, such as a radionuclide, can be used for imaging. Biologically active antibody fragments or humanized monoclonal antibodies, may be preferred for imaging use.
A patient's neoplastic tissue can be identified as, for example, sites of transformed stem cells, of tumors and locations of any metastases. Antibodies, appropriately labeled or linked to an imaging agent, can be injected in a physiologically acceptable carrier into a patient, and the binding of the antibodies can be detected by a method appropriate to the label or imaging agent, for example, by scintigraphy.
Antisense MN Nucleic Acid Sequences
MN genes are herein considered putative oncogenes and the encoded proteins thereby are considered to be putative oncoproteins. Antisense nucleic acid sequences substantially complementary to mRNA transcribed from MN genes, as represented by the antisense oligodeoxynucleotides ODN1 and ODN2 [SEQ. ID. NOS.: 3 and 4] can be used to reduce or prevent expression of the MN gene. [Zamecnick, P. C., pp. 1-6, Prospects for Antisense Nucleic Acid Therapy of Cancer and AIDS, (Wiley-Liss, Inc., New York, N.Y., USA; 1991); Wickstrom, E., pp. 7-24, id.; Leserman et al., pp. 25-34, id.; Yokoyama, K., pp. 35-52, id.; van den Berg et al., pp. 63-70, id.; Mercola, D., pp. 83-114, id.; Inouye, Gene, 72: 25-34 (1988); Miller and Ts'o, Ann. Reports Med. Chem., 23: 295-304 (1988); Stein and Cohen, Cancer Res., 48: 2659-2668 (1988); Stevenson and Inversen, J. Gen. Virol., 70: 2673-2682 (1989); Goodchild, pp. 53-77, Oligodeoxynucleotides: Antisense Inhibitors of Gene Expression (Cohen, J. S., ed; CRC Press, Boca Raton, Fla., USA; 1989); Dervan et al., pp. 197-210, id.; Neckers, L. M., pp. 211-232, id.; Leitner et al., PNAS (USA), 87: 3430-3434 (1990); Bevilacqua et al., PNAS (USA), 85: 831-835 (1988); Loke et al. Curr. Top. Microbiol. Immunol., 141: 282-288 (1988); Sarin et al., PNAS (USA), 85: 7448-7451 (1988); Agrawal et al., "Antisense Oligonucleotides: A Possible Approach for Chemotherapy and AIDS," International Union of Biochemistry Conference on Nucleic Acid Therapeutics (Jan. 13-17, 1991; Clearwater Beach, Fla., USA); Armstrong, L., Ber. Week, pp. 88-89 (Mar. 5, 1990); and Weintraub et al., Trends, 1: 22-25 (1985).] Such antisense nucleic acid sequences, preferably oligonucleotides, by hybridizing to the MN mRNA, particularly in the vicinity of the ribosome binding site and translation initiation point, inhibits translation of the mRNA. Thus, the use of such antisense nucleic acid sequences may be considered to be a form of cancer therapy.
Preferred antisense oligonucleotides according to this invention are gene-specific ODNs or oligonucleotides complementary to the 5' end of MN mRNA. Particularly preferred are the 29-mer ODN1 and 19-mer ODN2 [SEQ. ID. NOS.: 3 and 4]. Those antisense ODNs are representative of the many antisense nucleic acid sequences that can function to inhibit MN gene expression. Ones of ordinary skill in the art could determine appropriate antisense nucleic acid sequences, preferably antisense oligonucleotides, from the nucleic acid sequences of FIGS. 1 and 2.
Also, as described above, CGL3 cells transfected with an "antisense" MN cDNA/promoter construct, as well as SiHa and HeLa cells transfected with "antisense" MN cDNA, formed colonies much smaller than control CGL3 cells.
Vaccines
It will be readily appreciated that MN proteins and polypeptides of this invention can be incorporated into vaccines capable of inducing protective immunity against neoplastic disease and a dampening effect upon tumorigenic activity. Efficacy of a representative MN fusion protein GEX-3X-MN as a vaccine in a rat model is shown in Example 2.
MN proteins and/or polypeptides may be synthesized or prepared recombinantly or otherwise biologically, to comprise one or more amino acid sequences corresponding to one or more epitopes of the MN proteins either in monomeric or multimeric form. Those proteins and/or polypeptides may then be incorporated into vaccines capable of inducing protective immunity. Techniques for enhancing the antigenicity of such polypeptides include incorporation into a multimeric structure, binding to a highly immunogenic protein carrier, for example, keyhole limpet hemocyanin (KLH), or diptheria toxoid, and administration in combination with adjuvants or any other enhancers of immune response.
Preferred MN proteins/polypeptides to be used in a vaccine according to this invention would be genetically engineered MN proteins. Preferred recombinant MN protein are the GEX-3X-MN, MN 20-19, MN-Fc and MN-PA proteins.
Other exemplary vaccines include vaccinia-MN (live vaccinia virus with full-length MN cDNA), and baculovirus-MN (full length MN cDNA inserted into baculovirus vector, e.g. in suspension of infected insect cells). Different vaccines may be combined and vaccination periods can be prolonged.
A preferred exemplary use of such a vaccine of this invention would be its administration to patients whose MN-carrying primary cancer had been surgically removed. The vaccine may induce active immunity in the patients and prevent recidivism or metastasis.
It will further be appreciated that anti-idiotype antibodies to antibodies to MN proteins/polypeptides are also useful as vaccines and can be similarly formulated.
An amino acid sequence corresponding to an epitope of an MN protein/polypeptide either in monomeric or multimeric form may also be obtained by chemical synthetic means or by purification from biological sources including genetically modified microorganisms or their culture media. [See Lerner, Sci. Am. 248(2): 66-74 (1983).] The protein/polypeptide may be combined in an amino acid sequence with other proteins/polypeptides including fragments of other proteins, as for example, when synthesized as a fusion protein, or linked to other antigenic or non-antigenic polypeptides of synthetic or biological origin. In some instances, it may be desirable to fuse a MN protein or polypeptide to an immunogenic and/or antigenic protein or polypeptide, for example, to stimulate efficacy of a MN-based vaccine.
The term "corresponding to an epitope of an MN protein/polypeptide" will be understood to include the practical possibility that, in some instances, amino acid sequence variations of a naturally occurring protein or polypeptide may be antigenic and confer protective immunity against neoplastic disease and/or anti-tumorigenic effects. Possible sequence variations include, without limitation, amino acid substitutions, extensions, deletions, truncations, interpolations and combinations thereof. Such variations fall within the contemplated scope of the invention provided the protein or polypeptide containing them is immunogenic and antibodies elicited by such a polypeptide or protein cross-react with naturally occurring MN proteins and polypeptides to a sufficient extent to provide protective immunity and/or anti-tumorigenic activity when administered as a vaccine.
Such vaccine compositions will be combined with a physiologically acceptable medium, including immunologically acceptable diluents and carriers as well as commonly employed adjuvants such as Freund's Complete Adjuvant, saponin, alum, and the like. Administration would be in immunologically effective amounts of the MN proteins or polypeptides, preferably in quantities providing unit doses of from 0.01 to 10.0 micrograms of immunologically active MN protein and/or polypeptide per kilogram of the recipient's body weight. Total protective doses may range from 0.1 to about 100 micrograms of antigen. Routes of administration, antigen dose, number and frequency of injections are all matters of optimization within the scope of the ordinary skill in the art.
The following examples are for purposes of illustration only and not meant to limit the invention in any way.
EXAMPLE 1
Immunohistochemical Staining of Tissue Specimens
To study and evaluate the tissue distribution range and expression of MN proteins, the monoclonal antibody M75 was used to stain immunohistochemically a variety of human tissue specimens. The primary antibody used in these immunohistochemical staining experiments was the M75 monoclonal antibody. A biotinylated second antibody and streptavidin-peroxidase were used to detect the M75 reactivity in sections of formalin-fixed, paraffin-embedded tissue samples. A commercially available amplification kit, specifically the DAKO LSAB.TM. kit [DAKO Corp., Carpinteria, Calif. (USA)] which provides matched, ready made blocking reagent, secondary antibody and steptavidin-horseradish peroxidase was used in these experiments.
M75 immunoreactivity was tested according to the methods of this invention in multiple-tissue sections of breast, colon, cervical, lung and normal tissues. Such multiple-tissue sections were cut from paraffin blocks of tissues called "sausages" that were purchased from the City of Hope [Duarte, Calif. (USA)]. Combined in such a multiple-tissue section were normal, benign and malignant specimens of a given tissue; for example, about a score of tissue samples of breast cancers from different patients, a similar number of benign breast tissue samples, and normal breast tissue samples would be combined in one such multiple-breast-tissue section. The normal multiple-tissue sections contained only normal tissues from various organs, for example, liver, spleen, lung, kidney, adrenal gland, brain, prostate, pancreas, thyroid, ovary, and testis.
Also screened for MN gene expression were multiple individual specimens from cervical cancers, bladder cancers, renal cell cancers, and head and neck cancers. Such specimens were obtained from U.C. Davis Medical Center in Sacramento, Calif. and from Dr. Shu Y. Liao [Department of Pathology; St. Joseph Hospital; Orange, Calif. (USA)].
Controls used in these experiments were the cell lines CGL3 (H/F-T hybrid cells) and CGL1 (H/F-N hybrid cells) which are known to stain respectively, positively and negatively with the M75 monoclonal antibody. The M75 monoclonal antibody was diluted to a 1:5000 dilution wherein the diluent was either PBS [0.05 M phosphate buffered saline (0.15 M NaCl), pH 7.2-7.4] or PBS containing It protease-free BSA as a protein stabilizer.
Immunohistochemical Staining Protocol
The immunohistochemical staining protocol was followed according to the manufacturer's instructions for the DAKO LSAB.TM. kit. In brief, the sections were dewaxed, rehydrated and blocked to remove non-specific reactivity as well as endogenous peroxidase activity. Each section was then incubated with dilutions of the M75 monoclonal antibody. After the unbound M75 was removed by rinsing the section, the section was sequentially reacted with a biotinylated antimouse IgG antibody and streptavidin conjugated to horseradish peroxidase; a rinsing step was included between those two reactions and after the second reaction. Following the last rinse, the antibody-enzyme complexes were detected by reaction with an insoluble chromogen (diaminobenzidine) and hydrogen peroxide. A positive result was indicated by the formation of an insoluble reddish-brown precipitate at the site of the primary antibody reaction. The sections were then rinsed, counterstained with hematoxylin, dehydrated and cover slipped. Then the sections were examined using standard light microscopy.
Interpretation. A deposit of a reddish brown precipitate over the plasma membrane was taken as evidence that the M75 antibody had bound to a MN antigen in the tissue. The known positive control (CGL3) had to be stained to validate the assay. Section thickness was taken into consideration to compare staining intensities, as thicker sections produce greater staining intensity independently of other assay parameters.
Results
Preliminary examination of cervical specimens showed that 62 of 68 squamous cell carcinoma specimens (91.2%) stained positively with M75. Additionally, 2 of 6 adenocarcinomas and 2 of 2 adenosquamous cancers of the cervix also stained positively. In early studies, 55.6% (10 of 18) of cervical dysplasias stained positively. A total of 9 specimens including both cervical dysplasias and tumors, exhibited some MN expression in normal appearing areas of the endocervical glandular epithelium, usually at the basal layer. In some specimens, whereas morphologically normal-looking areas showed expression of MN antigen, areas exhibiting dysplasia and/or malignancy did not show MN expression.
M75 positive immunoreactivity was most often localized to the plasma membrane of cells, with the most apparent stain being present at the junctions between adjacent cells. Cytoplasmic staining was also evident in some cells; however, plasma membrane staining was most often used as the main criterion of positivity.
M75 positive cells tended to be near areas showing keratin differentiation in cervical specimens. In some specimens, positive staining cells were located in the center of nests of non-staining cells. Often, there was very little, if any, obvious morphological difference between staining cells and non-staining cells. In some specimens, the positive staining cells were associated with adjacent areas of necrosis.
In most of the squamous cell carcinomas of the cervix, the M75 immunoreactivity was focal in distribution, i.e., only certain areas of the specimen stained. Although the distribution of positive reactivity within a given specimen was rather sporadic, the intensity of the reactivity was usually very strong. In most of the adenocarcinomas of the cervix, the staining pattern was more homogeneous, with the majority of the specimen staining positively.
Among the normal tissue samples, intense, positive and specific M75 immunoreactivity was observed only in normal stomach tissues, with diminishing reactivity in the small intestine, appendix and colon. No other normal tissue stained extensively positively for M75. Occasionally, however, foci of intensely staining cells were observed in normal intestine samples (usually at the base of the crypts) or were sometimes seen in morphologically normal appearing areas of the epithelium of cervical specimens exhibiting dysplasia and/or malignancy. In such, normal appearing areas of cervical specimens, positive staining was seen in focal areas of the basal layer of the ectocervical epithelium or in the basal layer of endocervical glandular epithelium. In one normal specimen of human skin, cytoplasmic MN staining was observed in the basal layer. The basal layers of these epithelia are usually areas of proliferation, suggesting the MN expression may be involved in cellular growth. In a few cervical biopsied specimens, MN positivity was observed in the morphologically normal appearing stratified squamous epithelium, sometimes associated with cells undergoing koilocytic changes.
Some colon adenomas (4 of 11) and adenocarcinomas (9 of 15) were positively stained. One normal colon specimen was positive at the base of the crypts. Of 15 colon cancer specimens, 4 adenocarcinomas and 5 metastatic lesions were MN positive. Fewer malignant breast cancers (3 of 25) and ovarian cancer specimens (3 of 15) were positively stained. Of 4 head and neck cancers, 3 stained very intensely with M75.
Although normal stomach tissue was routinely positive, 4 adenocarcinomas of the stomach were MN negative. Of 3 bladder cancer specimens (1 adenocarcinoma, 1 non-papillary transitional cell carcinoma, and 1 squamous cell carcinoma), only the squamous cell carcinoma was MN positive. Approximately 40% (12 of 30) of lung cancer specimens were positive; 2 of 4 undifferentiated carcinomas; 3 of 8 adenocarcinomas; 2 of 8 oat cell carcinomas; and, 5 of 10 squamous cell carcinomas. One hundred percent (4 of 4) of the renal cell carcinomas were MN positive.
In summary, MN antigen, as detected by M75 and immunohistochemistry in the experiments described above, was shown to be prevalent in tumor cells, most notably in tissues of cervical cancers. MN antigen was also found in some cells of normal tissues, and sometimes in morphologically normal appearing areas of specimens exhibiting dysplasia and/or malignancy. However, MN is not usually extensively expressed in most normal tissues, except for stomach tissues where it is extensively expressed and in the tissues of the lower gastrointestinal tract where it is less extensively expressed. MN expression is most often localized to the cellular plasma membrane of tumor cells and may play a role in intercellular communication or cell adhesion. Representative results of experiments performed as described above are tabulated in Table 2.
The results recorded in this example indicate that the presence of MN proteins in a tissue sample from a patient may, in general, depending upon the tissue involved, be a marker signaling that a pre-neoplastic or neoplastic process is occurring. Thus, one may conclude from these results that diagnostic/prognostic methods that detect MN antigen may be particularly useful for screening patient samples for a number of cancers which can thereby be detected at a pre-neoplastic stage or at an early stage prior to obvious morphologic changes associated with dysplasia and/or malignancy being evident or being evident on a widespread basis.
EXAMPLE 2
Vaccine--Rat Model
As shown in Example 7 of WO 93/18152 (International Publication Date: Sep. 16, 1993), in some rat tumors, for example, the XC tumor cell line (cells from a rat rhabdomyosarcoma), a rat MN protein, related to human MN, is expressed. Thus a model was afforded to study antitumor immunity induced by experimental MN-based vaccines. The following representative experiments were performed.
Nine- to eleven-day-old Wistar rats from several families were randomized, injected intraperitoneally with 0.1 ml of either control rat sera (the C group) or with rat serum against the MN fusion protein GEX-3X-MN (the IM group). Simultaneously both groups were injected subcutaneously with 10.sup.6 XC tumor cells.
Four weeks later, the rats were sacrificed, and their tumors weighed. The results indicated that the difference between the two groups--C and IM--was significant by Mann-Whitney rank test (U=84, .alpha.<0.025). The IM group of baby rats developed tumors about one-half the size of the controls, and 5 of the 18 passively immunized rats developed no tumor at all, compared to 1 of 18 controls.
EXAMPLE 3
Transient Transformation of Mammalian Cells by MN Protein
This example (1) examines the biological consequences of transfecting human or mouse cells with MN-cDNA inserted into expression vectors, mainly from the viewpoint of the involvement of MN protein in oncogenesis; (2) determines if MN protein exerts carbonic anhydrase activity, and whether such activity is relevant for morphologic transformation of cells; and (3) tests whether MN protein is a cell adhesion molecule (CAM).
Synopsis
Methods: MN-cDNA was inserted into 3 expression vectors and was used for transfecting human or mouse cells. MN protein was detected by Western blotting, radioimmunoassay or immunoperoxidase staining; in all tests the MN-specific monoclonal antibody M75 (MAb M75) was used. Carbonic anhydrase activity was determined by the acidification velocity of carbonate buffer in CO.sub.2 atmosphere.
Results: (1) Cells (human CGL-1 and mouse NIH3T3 cells) transfected with MN-cDNA showed morphologic transformation, but reverted to normal phenotype after 4-5 weeks. (2) This reversion was not due to the loss, silencing or mutation of the MN insert. (3) MN protein has the enzyme activity of a carbonic anhydrase, which can be inhibited with acetazolamide; however, the inhibition of the carbonic anhydrase enzyme activity did not affect transformation. (4) MN protein is an adhesion protein, involved in cell-to-cell contacts.
Background
This example concerns transformation of mammalian cells by MN-cDNA inserted into expression vectors derived from retroviruses. Such vectors are suitable for efficient and stable integration into cellular DNA and for continuous expression of MN protein. Cells transfected with these constructs showed morphologic transformation, but after some time, they reverted to normal phenotype.
Sulfonamides, including acetazolamide, are very potent inhibitors of known carbonic anhydrases [Maren and Ellison, Mol. Pharmacol., 3: 503-508 (1967)]. Acetazolamide was tested to determine if it inhibited also the MN-carbonic anhydrase, and if so, whether inhibition of the enzyme affected cell transformation.
There are reasons to believe that MN protein could be involved in direct cell-to-cell interactions: A) previous observations indicated a functional resemblance of MN protein to surface glycoproteins of enveloped viruses, which mediate virus adsorption to cell surface receptors, and MN participated in the formation of phenotypically mixed virions of vesicular stomatitis virus. B) Inducibility of MN protein expression by growing HeLa cells in densely packed monolayers suggests that it may be involved in direct interactions between cells. C) Finally, there is a structural similarity between the MN protein and receptor tyrosine phosphatase .beta., which also contains proteoglycan and carbonic anhydrase domains; those domains mediate direct contacts between cells of the developing nervous system [Peles et al., Cell, 82: 251-260 (1995)]. Therefore, MN protein was tested to see if it bound to cell surface receptors; the result was clearly positive that it does.
Materials and Methods
Cell Lines
Cells used in this example were: CGL1 and CGL3--respectively non-tumorigenic and tumorigenic HeLa x fibroblast hybrids [Stanbridge et al., Somat. Cell Genet., 7: 699-712 (1981)], mouse cell line NIH3T3, HeLa cells and monkey Vero cells. The NIH3T3 cells were seeded at very low density to obtain colonies started from single cells. The most normal appearing colony, designated subclone 2, was picked for use in the experiments reported in this example.
Expression Vectors
Full-length MN cDNA was acquired from a pBluescript subclone [Pastorek et al., Oncogene, 9: 2877-2888 (1994)]. To remove 5' and 3' noncoding sequences, that might reduce subsequent gene expression, a polymerase chain reaction (PCR) was performed. The 5' primer TAGACAGATCTACGATGGCTCCCCTGTGCCCCAG [SEQ. ID. NO.: 88] encompasses a translation start site and Bg1II cloning site, and the 3' primer ATTCCTCTAGACAGTTACCGGCTCCCCCTCAGAT [SEQ. ID. NO.: 89] encompasses a stop codon and XbaI cloning site. Full-length MN-cDNA as a template and Pfu DNA Polymerase [Stratagene; LaJolla, Calif. (USA)] were used in the reaction.
The PCR product was sequenced and found to be identical with the template; it carried no mutations. The PCR product harbouring solely the MN coding sequence was inserted into three vectors: 1. pMAMneo [Clontech; Palo Alto, Calif. (USA)] plasmid allowing dexamethasone-inducible expression driven by the MMTV-Long Terminal Repeat (LTR) promoter and containing a neo gene for selection of transformants in media supplemented with Geneticin (G418) antibiotics. 2. Retroviral expression vector pGD [Daley et al., Science, 247: 824-829 (1990); kindly provided by Prof. David Baltimore, New York-Cambridge)] containing MLV-LTR promoter and neo gene for G418 antibiotics selection. 3. Vaccinia virus expression vector pSC11 [Chakrabarti et al., Mol. Cell. Biol., 5: 3403-3409 (1985)]. Transfection was performed via a calcium-phosphate precipitate according to Sambrook et al. (eds.), Molecular cloning. A laboratory manual, 2nd ed., Cold Spring Harbor Laboratory Press (1989).
Vaccinia virus strain Praha clone 13 was used as parental virus [Kutinova et al., Vaccine, 13: 487-493 (1995)]. Vaccinia virus recombinant was prepared by a standard procedure [Perkus et al., Virology, 152: 285-297 (1986)]. Recombinant viruses were selected and plaque purified twice in rat thymidine-kinase-less RAT2 cells [Topp, W. C., Virology, 113: 408-411 (1981)] in the presence of 5'-bromodeoxyuridine (100 .mu.g/ml). Blue plaques were identified by overlaying with agar containing 5-bromo-4-chloro-3-indolyl-.beta.-D-galactopyranoside (X-Gal) (200 .mu.g/ml).
CA Assay
Carbonic anhydrase activity was measured by a micro-method [Brion et al., Anal. Biochem., 175: 289-297 (1988)]. In principle, velocity of the reaction CO.sub.2 +H.sub.2 .fwdarw.H.sub.2 CO.sub.3 is measured by the time required for acidification of carbonate buffer, detected with phenol red as a pH indicator. This reaction proceeds even in absence of the enzyme, with t.sub.0 =control time (this was set to 60 seconds). Carbonic anhydrase reduces the time of acidification to t; one unit of the enzyme activity reduces the time to one half of control time: t/t.sub.0 =1/2.
For the experiment, MN protein was immunoprecipitated with Mab M75 from RIPA buffer (1% Triton X-100, 0.1% deoxycholate, 1 mM phenylmethylsulfonylfluoride and 200 trypsin-inhibiting units/ml of Trasylol in PBS, pH 7.2) extract of Vero cells infected with vaccinia-MN construct, after the cells developed cytopathic effect, or with "empty" vaccinia as a control. The MN+antibody complex was subsequently adsorbed to protein A--Staphylococcus aureus cells [Kessler, S. W., J. Immunol., 115: 1617-1624 (1975)] and rinsed 2.times. with PBS and 2.times. with 1 mM carbonate buffer, pH 8.0. The precipitate was resuspended in the same buffer and added to the reaction mixture. Acetazolamide (Sigma) was tested for inhibition of carbonic anhydrase [Maren and Ellison, supra]. In extracts of infected cells used for immunoprecipitation, the concentration of total proteins was determined by the Lowry method [Lowry et al., J. Biol. Chem., 193: 265-275 (1951)] and that of MN protein by a competition radioimmunoassay as described in Zavada et al., Int. J. Cancer, 54: 268-274 (1993).
Western Blots
Western blotting and development of the blots using .sup.125 I-labelled M75 and autoradiography was performed as before [Pastorekova et al., Virology, 187: 620-626 (1992); and Zavada (1993), supra].
Adhesion Assay
For the adhesion assay [Hoffman S., "Assays of cell adhesion," IN: Cell-cell Interactions, (Stevenson et al. eds.) pp. 1-30 (IRL Press at Oxford University Press; Oxford, N.Y., Tokyo; 1992)], 25 .mu.l aliquots MN protein (affinity purified pGEX-3X MN) [Zavada et al. (1993), supra] or of control proteins were spotted on 5 cm-diameter bacteriological Petri dishes and allowed to bind for 2 hours at room temperature. This yielded circular protein-coated areas of 4-5 mm diameter. MN protein was diluted to 10 .mu.g/ml in 50 mM carbonate buffer, pH 9.2. Patches of adsorbed control proteins were prepared similarly. Those included collagens type I and IV, fibronectin, laminin and gelatin (Sigma products), diluted and adsorbed according to the manufacturer's recommendations; FCS and BSA were also included. After aspiration of the drops, the dishes were rinsed 2.times. with PBS and saturated for 1 hour with DMEM supplied with 5% FCS. The plates were seeded with 5.times.10.sup.5 cells in 5 ml of DMEM+5% FCS and incubated overnight at 37.degree. C. The plates were rinsed with PBS, and the attached cells were fixed with formaldehyde, post-fixed with methanol and Giemsa stained.
Results
1. Transformation and reversion of CGL1 cells transfected with MN-cDNA
Since the expression of MN protein correlated with the tumorigenicity of HeLa.times.fibroblast hybrids [Zavada et al. (1993), supra], the non-tumorigenic hybrid CGL1 cells were first tested. Those cells, transfected with the pMAM.MN construct, after selection with Geneticin, formed colonies with varying degrees of transformation; some of them appeared normal. While normal CGL1 cells are contact inhibited, growing in a parallel orientation, the transformed cells formed very dense colonies, showing the loss of contact inhibition. Such colonies grew more slowly than the original CGL 1.
After subcloning, the cells isolated from transformed colonies segregated revertants. The reversion was a gradual, step-wise process; there were colonies with different degrees of reversion. After 2 passages, all the cell population became a morphologically indistinguishable from normal CGL1. This was due to the reversion of some cells and to the selective advantage of the revertants, which grew faster than the transformed cells. Despite repeated attempts, not even one single stably transformed cell clone was obtained. No transformed colonies were found in CGL1 cells transfected with an "empty" pMAM control plasmid.
Growth of the CGL1+pMAM.MN revertants in media supplied with 5 .mu.g/ml of dexamethasone for 7 days enhanced the production of MN protein, but the morphology of the cells did not return to transformed.
2. Rescue of transforming MN from the revertants
The reversion of MN-transformed cells to normal phenotype could have at least 4 causes: A) loss of the MN insert; B) silencing of the MN insert, e.g., by methylation; C) mutation of the MN insert; D) activation of a suppressor gene, coding for a product which neutralizes transforming activity of MN protein; E) loss of a MN-binding protein. To decide among those alternatives, the following experiment was designed as graphically outlined in FIG. 9.
MN-cDNA was inserted into pGD, a vector derived from mouse leukemia virus--MLV. A defective virus was thereby engineered, which contained the MN gene and the selective marker neo instead of genes coding for viral structural proteins. With this construct, mouse NIH3T3 cells were transfected. In media supplied with Geneticin, the cells formed colonies with phenotypes ranging from strongly transformed to apparently normal. All of the transformed colonies and about 50% of the normal colonies expressed MN protein. Contrasting with normal NIH3T3 cells, the transformants were also able to form colonies in soft agar, reflective of the loss of anchorage dependence, characteristic of cell transformation. Upon passaging, the cells isolated from transformed colonies reverted to normal morphology, and at the same time, they lost the capacity to form colonies in soft agar, while still expressing the MN protein. This permanent presence of MN protein in revertants ruled out alternatives A) and B) supra, that is, loss or silencing of the MN gene as a cause of reversion.
To decide among the other 3 alternatives, the revertants were superinfected with live, replication competent MLV. This virus grows in NIH3T3 cells without any morphologic manifestations, and it works as a "helper" for the pGD.MN construct. Virus progeny from MLV-infected revertants represents an artificial virus complex [PGD.MN +MLV]. This consists of 2 types of virions: of standard type MLV particles and virions containing the PGD.MN genome, enveloped in structural proteins provided by the "helper" virus. This virus complex was infectious for fresh NIH3T3 cells; it again induced in them morphologic transformation and the capacity to form agar colonies.
Contrasting with NIH3T3 transfected with pGD.MN, all the colonies of cells infected with [pGD.MN+MLV] complex, which grew in the presence of Geneticin, were uniformly transformed and contained MN proteins. The transformants once more reverted to normal phenotype although they kept producing infectious [pGD.MN +MLV] complex, which induced transformation in fresh NIH3T3 cells. This cycle of infection-transformation-reversion was repeated 3 times with the same result. This ruled out alternative C)--mutation of MN-cDNA as a cause of reversion.
Normal NIH3T3 cells formed a contact inhibited monolayer of flat cells, which did not stain with Mab M75 and immunoperoxidase. Cells infected with [pGD.MN+MLV] complex were clearly transformed: they grew in a chaotic pattern and showed loss of contact inhibition. Some of the cells showed signs of apoptosis. Two passages later, the cell population totally reverted to original phenotype as a result of frequent emergence of revertants and of their selective advantages (faster growth and a higher efficiency of plating). In fact, the revertants appeared to grow to a somewhat lower saturation density than the original NIH3T3 cells, showing a higher degree of contact inhibition.
The control NIH3T3 cells did not contain any MN protein (Western blot); while both transformed cells and revertants contained the same amount and the same proportion of 54 and 58 kDa bands of MN protein. In a non-reducing gel, MN protein was present in the form of oligomers of 153 kDa. Consistently, by competition RIA, approximately 40 ng MN/mg total protein was found in both of the transformed cells and revertants.
3. Carbonic Anhydrase Activity and its Inhibition
Since the carbonic anhydrase domain represents a considerable part of the MN protein (see FIG. 8), tests were performed to determine whether it is indeed enzymatically active. Vero cells infected with the vaccinia.MN construct, which contained more of the MN protein than other cells used in the present experiments, served as a source of MN protein. The cells were extracted with RIPA buffer, and MN protein was concentrated and partially purified by precipitation with MAb M75 and SAC. The immunoprecipitate was tested for CA activity. 78 .mu.l of precipitate contained 1 unit of the enzyme. From the extract, the concentration of total proteins and of MN protein was determined; 1 unit of enzyme corresponded to 145 ng of MN protein or to 0.83 mg of total protein. The immunoprecipitate from Vero cells infected with control virus had no enzyme activity.
Activity of MN carbonic anhydrase was inhibited by acetazolamide; 1.53.times.10.sup.-8 M concentration of the drug reduced enzyme activity to 50%.
Preliminary tests showed that confluent cultures of HeLa or of NIH3T3 cells tolerated 10.sup.-5 -10.sup.-3 M concentration of acetazolamide for 3 days without any signs of toxicity and without any effect on cell morphology. In sparse cultures, 10.sup.-5 M acetazolamide did not inhibit cell growth, but 10.sup.-4 M already caused a partial inhibition. Thus, 10.sup.-5 M acetazolamide was added to NIH3T3 cells freshly transformed with the [pGD.MN+MLV] complex. After 4 days of incubation, the colonies were fixed and stained. No difference was seen between cells growing in the presence or absence of acetazolamide; both were indistinguishable from correctly transformed NIH3T3 cells. Thus, the enzymatic activity of carbonic anhydrase is not relevant for the transforming activity of MN protein.
4. Cell Adhesion Assay
To determine whether or not MN protein is a cell adhesion molecule (CAM), adhesion assays were performed in plastic bacteriological Petri dishes (not treated for use with tissue culture). Cells do not adhere to the surfaces of such dishes, unless the dishes are coated with a binding protein. NIH3T3 cells adhered, spread and grew on patches of adsorbed MN protein. Only very few cells attached outside the areas coated with MN protein.
Other variants of the experiment demonstrated that NIH3T3 cells adhered and spread on patches of adsorbed collagen I and IV, fibronectin and laminin. NIH3T3 cells did not attach to dots of adsorbed gelatin, FCS or BSA.
CGL1, HeLa and Vero cells also adhered to MN protein, but 3 leukemia cell lines showed no adherence. CGL3 cells, strongly expressing MN protein; adhered less efficiently to MN protein dots then did CGL1. Blocking of the adsorbed MN protein with an excess of MAb M75 did not abrogate the adhesion of NIH3T3 cells. Also, the presence of 10.sup.-4 M acetazolamide in the media did not affect the cell adhesion.
To confirm the specificity of adhesion, MN protein was absorbed with SAC loaded with MAb M75 (directed to MN) or MAb M67, directed to an unrelated antigen (Pastorekova et al., supra), before it was applied to the surface of the Petri dishes. Absorption with the SAC-M75 complex totally abrogated the cell binding activity, whereas absorption with SAC-M67 was without any effect.
Discussion
The data provided herein is consistent with the view that the MN gene most likely represents a novel type of oncogene or proto-oncogene. MN protein has a very strong association with certain types of human carcinomas, and is absent from almost all normal tissues (except as shown in Examples 4-7 infra). Cells are morphologically transformed by MN-cDNA, such transformation being characterized by increased cell density, a criss-cross pattern of cell growth and the acquisition of the capacity to form colonies in soft agar (Pastorek et al., supra). Those features are characteristic of cells transformed with tumor viruses or with cloned oncogenes [Todaro et al., PNAS (USA) 51: 66-73 (1964); Macpherson and Montagnier, Virology, 23: 291-294 (1964)].
Adhesion molecules mediate cell-to-cell or cell to extracellular matrix binding; they play an essential role in embryogenesis and in cell growth and differentiation. Recent data has demonstrated that besides their mechanical function, some CAMs are also involved in signal transduction cascades. Their up-regulation or ectopic expression leads to disruption of the normal program of cell differentiation. CAMs are believed to play a role in invasion and metastasis as well as in the early steps of carcinogenesis [Pigott and Power, The Adhesion Molecule (Academic Press, London (1993); Rosales et al., Biochem. Biophys. Acta, 1242: 77-98 (1995)]. Therefore, the present finding of MN being an adhesion molecule appears very plausible. The development of tumors is generally a multi-step process; in cervical carcinomas, papillomaviruses certainly play an important rule [Zur Hausen et al., Virology, 184: 9-13 (1991)]. The ectopic expression of MN protein could represent an additional step. A third factor participating in the genesis of cervical carcinomas is most likely the loss or inactivation of tumor suppressor genes.
The extracellular part of MN protein contains domains homologous to proteoglycans and to CAs. Both of those are known to be engaged in cell-to-cell contacts, or in binding of cells to the extracellular matrix. Receptor protein tyrosine phosphatase .beta. is a cell membrane protein in embryo brains, binding by its CA domain to contactin on the surface of neurons, and by its proteoglycan domain to the glia [Peles et al., (1995) supra]. Another example is vaccinia virus, containing a CA domain in its surface glycoprotein, which is responsible for virus attachment to cellular receptors [Maa et al., J. Biol. Chem., 265: 1569-1577 (1990)]. Both of those structures related to CAs are enzymatically inactive. Due to mutations in the active center, they cannot bind Zn.sup.2+ ions, but its pocket-like structure was preserved, with potential to accommodate other ligands than CO.sub.2 +H.sub.2 O.
The CA and proteoglycan domains of the MN protein could, like in the above mentioned proteins, be involved in cell-to-cell interactions. Its deregulated expression could upset correct communication among cells. Years ago, contact inhibition was shown to be mediated by direct interactions between cells [Stoker, M. G. P., J. Cell. Sci., 2: 293-304 (1967], but its molecular mechanism has not been satisfactorily elucidated up to now. MN protein may interfere in signal transmission establishing contact inhibition.
Reversion of tumor cells to normal phenotype was first described in hamster cells transformed with Rous sarcoma virus. The cells changed their chaotic growth back to the original parallel array [Macpherson, I., Science, 148: 1731-1733 (1965)]. The src oncogene was transcriptionally silenced in segregated revertants. The provirus was shown to be methylated, and the methylation is known to prevent transcription [Searle et al., Nucl. Acid. Res., 12: 5193-5210 (1984)]. Reversion was also found in other tumor cells, which was again due to the methylation of the src gene [Hejnar et al., Cell Growth Differ., 5: 277-284 (1994)]. The frequency of reversion in those cases was of the order of 10.sup.-2 /cell/division.
Methylation of the MN insert was clearly not the cause of reversion in the system presented here, since the revertants contained the MN protein. In some instances, the reversion was explained by mutations of the src oncogene [Oppermann et al., Virology, 108: 47-70 (1981)], but in MN, mutation did not account for the reversion in MN-transformed cells.
All the MN-transformed cells revert within 4-5 weeks. A plausible (but not the only) explanation could be that the MN protein expressed in transfected cells, after some interval, switches on a suppressor gene(s), which code(s) for a hypothetical "normalizing" protein. This, in turn, neutralizes the transforming activity of the MN protein. This postulated suppressor gene is switched off in normal cells, not containing MN protein, and it is lost or inactivated in tumor cells.
Hybridization of HeLa cells with normal fibroblasts [Stanbridge et al., supra] indicated that HeLa cells express a critical oncogene, responsible for tumorigenicity in nude mice. This oncogene is counteracted by a tumor suppressor gene (or genes), which is absent or inactive in HeLa cells, but is functioning in fibroblasts. The original HeLa x fibroblast hybrid was non-tumorigenic, but it segregated clones with restored tumorigenicity. Tumorigenic segregants lost chromosome 11, containing the putative suppressor gene.
The MN protein is a candidate for being the product of the critical oncogene; its expression in the hybrids has been shown to correlate with their tumorigenicity [e.g., Zavada et al. (1993), supra]. The present results indicate that additional mechanisms might exist, which are able to "heal" a carcerous cell. Understanding the molecular mechanisms of action of MN protein in normal and in tumor cells and elucidating how the reversion works may provide new approaches to cancer therapy.
Prospects for therapy. There are many new principles of cancer therapy employing oncoproteins or molecules that interact with them as targets [Mendelsohn and Lippman, "Principles of molecular cell biology of cancer: growth factors," In: DeVita et al., eds., Cancer: principles and practice of oncology, pp. 114-133 4th ed., Philadelphia: Lippinocott (1993); DeVita et al., eds., Biologic therapy of cancer, 2nd ed., Philadelphia: Lippinocott (1995)]. The MN protein and at least some of its ligands (or receptors) appear to be particularly suitable for such purposes. MN protein is located on the cell surface and is thus vulnerable. It is present in a high percentage of certain human tumors, but is normally expressed abundantly only in the gastric and gallbladder mucosa as shown infra.
EXAMPLE 4
Analysis of Stomach cDNA Sequence and Expression in Tissues of Human and Rat Alimentary Tracts
Materials and Methods
Cell Lines and Antibodies
Human KATO III cells, derived from a gastric carcinoma, and HeLa cells derived from a carcinoma of cervix uteri were grown in Dulbecco's MEM supplemented with 20% and 10% fetal calf serum (FCS), respectively. The human AGS cell line from a gastric adenocarcinoma was maintained in F-10 medium supplemented with 20% FCS. The murine monoclonal antibody M75 which recognizes the N-terminal domain of MN/CA IX was used. Polyclonal rabbit antiserum to human CA II has been produced and characterized by Parkkila et al., Histochemistry, 99: 37-41 (1993). The antiserum showed high isozyme specificity in dot and Western blottings and time-resolved fluoroimmunoassay [Id.; Parkkila et al., J. Histochem. Cytochem., 41: 751-757 (1993); Parkkila et al., Clin. Chem. Acta., 230: 81-89 (1994)].
Isolation and Sequence Analysis of Stomach MN/CA9 cDNA Clone
The cDNA library in Lambda gt11, derived from normal human stomach [Clontech; Palo Alto, Calif. (USA)] was screened by hybridization using HeLa MN/CA9 cDNA labeled with [.alpha.-.sup.32 P]dCTP as a probe. Several positive clones were isolated and analyzed. An insert of the longest clone was subcloned into pBluescript SK [Stratagene; La Jolla, Calif. (USA)] and sequenced by the dideoxy chain termination method using either universal primers or MN/CA9-specific primers and T7 sequencing kit [Pharmacia; Piscataway, N.J. (USA)]. All sequencing reactions were performed on both HeLa- and stomach-derived cDNA templates and run in parallel on sequencing gels to allow easy identification of any possible differences.
Preparation of Tissues
Adult Sprague-Dawley female rats were anesthetized with ether and sacrificed by decapitation. Human tissue samples were obtained alongside routine histopathological specimens during surgical operations carried out at Oulu University Hospital. Each tissue sample was divided into several small pieces 5-10 mm thick. The specimens were fixed for 6 hours in Carnoy's fluid (absolute ethanol+chloroform+glacial acetic acid 6:3:1). Then they were dehydrated and embedded in paraffin in a vacuum oven at +58.degree. C. 5 .mu.M sections were placed onto gelatine-coated microscope slides. Routine histological examination of the sections was performed after haematoxylin-eosin (H-E) staining.
Immunohistochemistry
The double immunofluorescence staining consisted of the following steps: (1) pretreatment with undiluted cow colostral whey for 40 minutes and rinsing in PBS; (2) simultaneous incubation for 1 hour in 1:10 diluted TC medium of M75 hybridoma and 1:100 diluted rabbit antiserum for CA II in 1% BSA-PBS; and (3) incubation with 1:50 diluted rhodamine-conjugated swine anti-rabbit IgG antibodies and 1:50 diluted fluorescein isothiocyanate (FITC)-conjugated goat anti-mouse IgG antibodies (Dakopatts; Copenhagen, Denmark) in 1% BSA-PBS. The sections were washed three times for 10 minutes after the incubation steps and finally mounted in Mowiol (Hoeschst; Frankfurt am Main, Germany) and viewed with a conventional epifluorescence microscope (Leitz Aristoplan; Wetzlar, Germany) and a confocal laser scanning microscope (Leitz CLSM; Leica Laser Technics, Germany) using an air-cooled argon-krypton laser (75 mW output). The specimens were excited with a laser beam at a wavelength of 568 nm (rhodamine, CA II) and 488 nm (FITC, MN/CA IX). The emission light was focused through a pinhole aperture. The full field was scanned in square image formats of 512.times.512 pixels and built-in software was used to reconstruct the images obtained from the confocal sections.
MN/CA IX was also located by the biotin-streptavidin complex method. The steps in the stainings were as follows: (1) pre-treatment of the sections with undiluted cow colostral whey for 40 minutes and rinsing in PBS; (2) incubation for 1 hour with the M75 hybridoma medium diluted 1:10 in 1% BSA-PBS; (3) treatment with cow colostral whey for 40 minutes and rinsing in PBS; (4) incubation for 1 hour with biotinylated rabbit anti-mouse IgG (Dakopatts) diluted 1:500 in 1% BSA-PBS; (5) treatment with cow colostral whey for 5 minutes and rinsing in PBS; (6) incubation for 30 minutes with peroxidase-conjugated streptavidin (Dakopatts) diluted 1:600 in PBS; (7) incubation for 2 minutes in DAB solution containing 9 mg 3,3,'-diaminobenzidine tetrahydrochloride (Fluka; Buchs, Switzerland) in 15 ml PBS plus 10 .mu.l 30% H.sub.2 O.sub.2. The sections were washed in PBS after incubation steps 2, 4 and 6. In the control stainings, the primary MAb M75 was omitted or nonimmune rabbit serum was used instead of the anti-CA II serum. All the incubations and washings were carried out at room temperature, and the sections were finally mounted in Permount [Fisher Scientific; Fair Lawn, N.J. (USA)]. The stained sections were examined and photographed with a Leitz Aristoplan microscope.
Immunoprecipation and Western Blotting
Stomach tissue samples from human, rat, guinea pig and chicken were rinsed in phosphate-buffered saline, homogenized and extracted in 10 volumes of RIPA buffer (PBS, pH 7.2 containing 1% Triton X-100, 0.1% sodium deoxycholate, 1 mM PMSF and 200 trypsin-inhibiting units of Trasylol per ml). The extracts were clarified by centrifugation (5 min, 15,000 rpm) and immunoprecipitated with M75 MAb bound to Protein A of S. aureus in order to concentrate MN/CA IX proteins. After SDS-PAGE separation, the proteins were blotted onto Hybond C extra membrane [Amersham; Aylesbury, Bucks, England]. Then the membrane was incubated with .sup.125 I-labeled MAb M75 and subjected to autoradiography. Protein extracts from human cell lines were analyzed by Western blotting without preceding immunoprecipitation, using MAb M75 and an ECL detection system (Amersham).
Results
Sequence of MN/CA9 cDNA Isolated from Human Stomach Library
To detect possible differences between the MN/CA IX proteins associated with normal and cancerous tissues, respectively, MN/CA9 cDNA was cloned from the human stomach library. The stomach cDNA clone was sequenced along with the cDNA clone derived before from HeLa cells [Pastorek et al., supra; Opavsky et al., supra]. The sequence analysis revealed that the stomach cDNA clone is by 30 nt longer at the 5' end than the HeLa cDNA clone, thus possessing a leader sequence of 42 bp. This is, however, in good agreement with the data obtained by RNase protection assay [Opavsky et al., supra], using MN/CA9 RNA and a genomic clone derived from HeLa cells, which placed the major transcription start site of the MN/CA9 gene 42 bp upstream of the translation initiation codon. The nucleotide sequence of the 5' leader of stomach cDNA is identical to the HeLa-derived leader sequence. Also the coding sequence and the sequence of the 3' untranslated region of stomach cDNA show 100% identity with the HeLa cDNA sequence (EMBL Accession No. X66839).
Expression of the MN/CA IX Protein in Stomachs of Different Vertebrates
The inventors have shown before that the MN/CA9 gene is conserved in several vertebrate genomes [Opavsky et al., supra]. Since the MN/CA IX protein is expressed in the mucosa of a normal human stomach, it was tempting to look at its expression also in stomachs of other vertebrates. For the Western blotting analysis of protein extracts from stomachs of different animals, MAb M75, which recognizes the N-terminal, CA-unrelated domain of the MN/CA IX protein and thus does not cross-react with any other CA isoenzymes, was used. Noteworthy, the epitope for M75 was conserved throughout vertebrate evolution and detected MN/CA IX protein in rat, guinea pig and chicken stomachs by Western blot.
Protein extracts prepared from human rat, guinea pig and chicken stomach tissue samples were immunoprecipitated with MAb M75 bound to Protein A of S. aureus, separated by SDS-PAGE, and analyzed by immunoblotting using .sup.125 I-labeled M75. Twin bands were seen at 54/58 kDa for each sample.
Immunohistochemical Analysis of MN/CA IX Distribution in Human and Rat Alimentary Tracts
To get more detailed insight into the distribution of MN/CA IX in human and rat alimentary tracts, both immunofluorescence and immunoperoxidase techniques were employed. The former enabled more precise localization analysis as well as double immunostaining for isoenzyme comparison by applying confocal laser scanning microscopy.
The results of the immunohistochemical analysis are summarized in Table 3. The stainings show striking regional differences in the MN/CA IX expression along the cranial-caudal axis of the gastrointestinal canal. No positive reaction was found in sections of human oral or esophageal epithelia. Strong signal for MN/CA IX appeared in sections of both human and rat stomachs. The reaction was present throughout the gastric mucosa, from gastric pits to deep gastric glands and confined to the basolateral surface of the epithelial cells. All the major cell types of the gastric epithelium, including surface epithelial cells, zymogen cells and parietal cells expressed MN/CA IX. On the contrary, CA II was present only in the surface epithelial cells of the gastric pit and neck regions and in the parietal cells of the gastric glands, but was absent from the zymogen cells. No signal was obtained using nonimmune rabbit antiserum instead of the CA II antiserum. No reaction was observed also when the primary antibodies for MN/CA IX were omitted from the staining procedure.
The intestinal epithelium seems to be another important source of MN/CA IX expression. In the rat intestines, epithelial staining was present in the duodenum and colon, but was absent from sections of jejunum and ileum. The positive signal was confined again to the basolateral surface of the epithelium while no staining was seen at the apical surface. The basolateral membranes of the epithelial cells were found to stain throughout the large intestine; the staining was most abundant in the proximal segment, but the signal intensity decreased in the middle and distal segments, decreasing considerably in the distal colon.
In the human intestines, a faint positive reaction was seen in the ileum and proximal colon, and the signal decreased again in the middle colon. The positive reaction of the human ileum and proximal colon was heterogenous, since some sections showed only a faint staining, while the signal was quite abundant in other ones.
Comparison of the stainings in the rat and human colon also revealed that the distribution of the MN/CA IX protein through the mucosal layer was different. In the rat colon, the positive signal was most intense in the surface epithelium, while the deep colonic glands remained negative or showed only a weak reaction. In the human colon, the staining intensity increased from the surface towards the base of the crypts of Lieberkuhn.
In the human ileum, positive reaction was seen at the basolateral surface of the epithelial cells located in the crypts of Lieberkuhn. The positive signal was quite abundant also in the crypt base of the human proximal colon but was faint in the luminal surface epithelium. Only a faint and scattered signal was seen in the middle segment of the human colon.
Immunohistochemical analysis of the cellular and subcellular distribution of MN/CA IX was also performed on rat and human major digestive glands. Sections from submandibular and parotid glands showed no signal for MN/CA IX. A faint positive reaction was seen in the epithelial cells of the human pancreatic ducts, but sections from rat pancreas remained negative. The staining of the human pancreatic ducts was confined to the basolateral plasma membrane; the zymogen cells remained unstained. Both human and rat bile ducts showed positive signal which was again located at the basolateral surface of the epithelial cells. Hepatocytes were devoid of staining.
In addition to the gastric and intestinal epithelium, the gallbladder epithelium seems to be the third abundant site of MN/CA IX expression. Both immunoperoxidase and immunofluorescence stainings showed intense signal at the basolateral surface of the epithelium. High magnification images also showed a faint cytosolic reaction.
The confocal laser scanning microscopy revealed that CA II and MN/CA IX co-occurred in gallbladder epithelial cells. The signal for MN/CA IX was mainly found at the basolateral surface of the epithelial cells, while CA II was primarily located in the cytoplasm of the cells.
Expression of MN/CA IX in Human Stomach Tumor Cell Lines and Tissue Specimens
MN/CA IX protein is present in several types of human carcinomas and absent from the corresponding normal tissues [Zavada et al., supra; Liao et al., supra]. On the other hand, it is expressed in normal human stomach and in some tissues of the alimentary tract. However, the status of MN/CA IX expression in gastrointestinal tumors had not been known. In an initial attempt to obtain relevant data, Western blotting analysis of proteins extracted from two gastric carcinoma cell lines, e.g., KATO III and AGS, was performed. MN/CA IX protein was found to be absent from AGS cells, and its level was found considerably diminished in KATO III cells, when compared to HeLa cells derived from a cervical carcinoma. In addition, mobility of MN/CA IX protein detected in KATO III cells is different from the protein expressed in HeLa cells, indicating its unusual processing.
Data obtained by immunohistochemical staining of several tissue samples supported the results of Western blotting. The intestinal metaplasia of the gastric mucosa showed a faint positive staining for MN/CA IX which is, however, considerably weaker than that of normal stomach mucosa. No positive reaction for MN/CA IX was seen in a sample from a gastric adenocarcinoma, while the neoplastic epithelial cells of the same sample showed intense signal for human CA II. Four additional samples of stomach carcinomas were found to be negative for MN/CA IX. These data indicates that the expression of MN/CA IX is lost or considerably reduced in stomach tumor cells.
Discussion
Expression of MN/CA IX in normal human stomach on the one hand, and in several carcinomas of other organs but not in the normal counterpart tissues on the other hand, raised several questions.
First of all, there was the question of whether there are any differences between the "normal" and "cancerous" MN/CA9 cDNA sequences, which could be implicated in the unusual expression pattern of MN/CA IX protein. Sequence comparison of the MN/CA9 cDNA clones derived from normal human stomach and HeLa cells, repectively, revealed no mutations in the coding region. Moreover, the size and nucleotide sequence of the stomach cDNA 5' leader is identical with the HeLa-derived leader estimated by RNase protection assay, suggesting that the expression of the MN/CA9 gene is driven from a single universal promoter. On the basis of these data, assumed was the involvement of other regulatory events (e.g. action of tissue-specific transcription factors) in control of MN/CA IX expression under normal conditions and during tumorigenesis. However, this assumption requires further investigation.
Since the MN/CA9 gene is present in genomes of different vertebrates, another question was whether it is actually expressed in the stomachs of those animals. It was found that besides human stomach, the MN/CA IX protein is detectable in the stomachs of the rat, guinea pig and chicken. This evolutionary conservation of MN/CA IX protein expression indicates its physiological significance.
Immunohistochemical analysis of MN/CA IX distribution in human and rat alimentary tracts and in human stomach carcinomas brought additional data in support of this view. MN/CA IX protein was found predominantly in the gastric mucosa and in gallbladder epithelium, as a part of basolateral membranes of epithelial cells. These tissues are known to express also other CAs, mainly the cytoplasmic CA II isoenzyme and CA IV isoenzyme associated with apical membranes of the gallbladder epithelium. They are involved in production of ions (HCO.sub.3.sup.- and H.sup.+) into the luminal space of the alimentary canal and in the protection of gastroduodenal cells from acidic pH. MN/CA IX protein may represent a complementary component of epithelial cells which participates in the physiological processes via enzyme activity of its CA domain. Facilitating CO.sub.2 transfer and translocation of H.sup.+ or HCO.sub.3.sup.- ions across the basolateral membranes, it may play a role in intracellular pH regulation.
However, basolateral localization of MN/CA IX protein also suggests its possible involvement in intercellular communication of epithelial cells and in maintenance of epithelial integrity. Density-inducible expression of MN/CA IX in HeLa cells enforces this idea [Pastorekova et al., supra]. The CA domain of MN/CA IX may be of significance also in this function via its putative ability to bind ligand/receptor molecules on neighboring cells. Recently, it was shown that the CA domain of protein tyrosine phosphatase RPTP-.beta., expressed in brain, mediates intercellular signalling through the functional binding to the neuronal-specific molecule contactin [Peles et al., Cell, 82: 251-260 (1995)]. By analogy, MN/CA IX biological activity may be connected with its partnership with other functionally important molecules. In fact, the existence of different partners in normal tissues and in tumors may create the basis for the differential expression of MN/CA IX.
Interestingly, no MN/CA IX protein or only reduced levels were detected in protein extracts from two gastric carcinoma cell lines and in several stomach tumor tissue specimens. There are only a few reports available on the expression of other carbonic anhydrase isoenzymes in gastrointestinal tumors [Shousha and Pestonjee, Arch. Pathol. Lab. Med., 111: 279-281 (1987); Parkkila et al., Histochem. J., 27: 133-138 (1995); Frazier et al., Pancreas, 5: 507-514 (1990); Mori et al., Gastroenterology, 195: 820-826 (1993); Gramlich et al., Arch. Pathol. Lab. Med., 114: 415-419 (1990)]. Some of them provide evidence of continuing expression of CA I an CA II in gastric and pancreatic carcinomas [Shousha and Pestonjee, supra; Parkkila et al. (1995), supra; Frazier et al., supra], while the other shows that the majority of colorectal cancers derived from CA I-positive cells do not express CA I [Mori et al., supra; Gramlich et al., supra]. However, except for MN/CA IX, no CA isoenzyme has been associated with tumors originating from CA-negative tissues.
In conclusion, data presented herein suggest that the MN/CA IX protein is required for the normal physiological function of gastrointestinal and gallbladder epithelia, and its decreased expression may be associated with human gastric carcinogenesis.
EXAMPLE 5
MN/CA IX Expression in Colorectal Tumors
In the normal human colon, MN/CA IX is expressed in the proliferating zone of the crypt epithelium with gradual decrease in the distal colorectum. This example provides a study of the expression of MN in a series of colorectal neoplasms.
Materials and Methods
Seventy-six colonic lesions were studied in the experiments recorded in this example as follows: 8 hyperplastic polyps, 1 juvenile polyp, 39 adenomas, 21 carcinomas and 7 metastases. Sections from formalin-fixed, paraffin-embedded specimens were stained with the M75 MAb, specific for MN, and a biotin-streptavidin complex method was used.
Results
The hyperplastic polyps showed moderate reaction in deep parts of the crypt epithelium. The juvenile polyp was negative. No staining was found in 21% of the adenomas, while 48% showed weak staining, and 31% showed moderate or strong staining, located mainly in the superficial parts. In carcinomas, no staining was seen in 24% of the cases, 29% showed weak staining, whereas 47% showed either moderate or strong staining. The most intense signal was seen in mucinous carcinoma. There was no relationship between the location of the tumors and the staining intensity. Four of the seven metastases showed positive staining.
Conclusion
The results show that the majority of colorectal tumors display abnormal expression of MN/CA IX. The experiments indicate that MN/CA IX is involved in the pathogenesis of colorectal neoplasia, and that it may be a marker of increased proliferation in colorectal mucosa.
EXAMPLE 6
Regional, Cellular and Subcellular Localization of MN/CA IX in the Human Gut
Carbonic anhydrases participate in regulatory acid-base and water balance in various tissues, including gastrointestinal tract epithelia and digestive glands. This example presents a study of immunohistochemical localization of MN/CA IX in the human gut, and compares its distribution to that of CAs I, II and IV, which are known to be expressed in the intestinal epithelium.
The MAb M75, specific for MN/CA IX as confirmed by Western blots and by the immunostaining of Cos-7 cells transfected with MN/CA IX cDNA, was used for the staining.
Immunohistochemical staining of the human gut revealed prominent staining for MN/CA IX in the epithelial cells of the duodenum and jejunum, the reaction being most intense in the crypts. A moderate reaction was also seen in the deep crypts of the ileal mucosa. MN/CA IX-positive staining was found in the cryptal epithelium of the large intestine, but it was generally weaker than in the small intestine. In all the segments, the MN/CA IX staining was confined to the basolateral surfaces of the epithelial cells.
The results indicate isozyme-specific regulation of MN/CA IX expression along the cranial-caudal axis of the human gut. Its regional and subcellular localization differs considerably from that of CA I, II and IV, which are expressed in the gastrointestinal canal. The unique localization of MN/CA IX in the basolateral surfaces is compatible with the theory that it has a physiological role in intercellular communication as well as in CO.sub.2 hydration.
EXAMPLE 7
Immunohistochemical Study of the Distribution of CAs I, II, IV, V, VI and MN/CA IX in the Human Intestine
This example presents an immunohistochemical comparison of the distribution of MN/CA IX and CAs I, II, IV, V and VI, and defines the cell types which express them.
Small Intestine
As indicated above in Example 6, prominent staining for MN/CA IX was found in the surface epithelial cells of the duodenum and jejunum, and a moderate reaction was seen in the deep crypts of the ileal mucosa. MN/CA IX expression was confined to the basolateral surfaces of the stained epithelial cells.
CA I was found in the deep crypts of Lieberkuhn of the jejunum and ileum. CA II appeared in the surface epithelium and Brunner's glands of the duodenum and the surface epithelium of the jejunum. The surface epithelial cells showed a positive staining for mitochondrial CA, CA V, in all segments. The subepithelial capillary endothelium contained both CA I and IV. No staining for secretory CA VI was seen in the small intestine.
Large Intestine
MN/CA IX gave a moderate reaction in the epithelial cells of the caecum and ascending colon, where the signal was confined to the basolateral surfaces of the epithelium and was most distinct in the deep intestinal glands. The expression of MN/CA IX seemed to be considerably weaker in the distal colon and rectum.
Intense cytoplasmic reactions for both CA I and II were detected in the surface, non-goblet epithelial cells throughout the large intestine. Anti-CA IV serum revealed a strong signal in the mucosal brush border of all segments studied. The subepithelial capillary endothelium expressed both CA I and IV. The most superficial epithelial cells lining the lumen also contained CA V throughout the large intestine. No signal for CA VI was detected.
The results indicate that CA isoenzymes are differentially expressed along the axis of the gastrointestinal canal. Several are expressed in the small and large intestine where they likely form complementary systems that participate in electrolyte and water transport.
ATCC Deposits. The materials listed below were deposited with the American Type Culture Collection (ATCC) at 12301 Parklawn Drive, Rockville, Md. 20852 (USA). The deposits were made under the provisions of the Budapest Treaty on the International Recognition of Deposited Microorganisms for the Purposes of Patent Procedure and Regulations thereunder (Budapest Treaty). Maintenance of a viable culture is assured for thirty years from the date of deposit. The hybridomas and plasmids will be made available by the ATCC under the terms of the Budapest Treaty, and subject to an agreement between the Applicants and the ATCC which assures unrestricted availability of the deposited hybridomas and plasmids to the public upon the granting of patent from the instant application. Availability of the deposited strain is not to be construed as a license to practice the invention in contravention of the rights granted under the authority of any Government in accordance with its patent laws.
The description of the foregoing embodiments of the invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teachings. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable thereby others skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.
All references cited herein are hereby incorporated by reference.
Claims
Post-issuance certificates present
The text shown below may not reflect later post-issuance changes.
We claim:
1. A method of screening for preneoplastic/neoplastic disease using a nucleic acid based assay comprising: (a) determining whether abnormal MN gene expression is present in a vertebrate; and (b) if abnormal MN gene expression is determined to be present in said vertebrate, determining that said vertebrate has a significant risk of having preneoplastic/neoplastic disease; wherein said MN gene encodes an MN protein that is encoded by a nucleic acid having a nucleotide sequence selected from the group consisting of: (a) SEQ ID NO: 1; (b) nucleotide sequences that hybridize under stringent conditions to complement of SEQ ID NO: 1; and (c) nucleotide sequences that differ from SEQ ID NO: 1 or from the nucleotide sequences of (b) in codon sequence due to the degeneracy of the genetic code.
2. The method according to claim 1 wherein said vertebrate is a mammal.
3. The method according to claim 1 wherein said vertebrate is a human.
4. The method according to claim 1 wherein said preneoplastic/neoplastic disease is selected from the group consisting of mammary, urinary tract, ovarian, uterine, cervical, endometrial, vaginal, vulval, prostate, liver, lung, skin, thyroid, pancreatic, testicular, brain, head and neck, mesodermal, gallbladder, rectal, duodenal, jejunal, ileal, gastric, pancreatic duct, liver duct, and colon preneoplastic/neoplastic diseases.
5. The method according to claim 1 wherein said preneoplastic/neoplastic disease is selected from the group consisting of mammary, bladder, renal, prostate, ovarian, cervical, endometrial, uterine, vaginal, vulval, lung, skin, thyroid, duodenal, jejunal, ileal, colon, rectal, liver, pancreatic, testicular, brain, head and neck and mesodermal preneoplastic/neoplastic diseases, wherein abnormal MN gene expression is determined to be present if the level of MN gene expression and/or the cellular location of said MN gene expression is or are not normal.
6. The method according to claim 1 wherein said preneoplastic/neoplastic disease is selected from the group consisting of gallbladder and gastric preneoplastic/neoplastic diseases, wherein the absence of MN gene expression or a level of MN gene expression below a normal level for a respective tissue is considered abnormal and signifies the presence of preneoplastic/neoplastic disease.
7. The method according to claim 3 wherein the preneoplastic/neoplastic disease is selected from the group consisting of gastric mucosa, gallbladder epithelium, small intestinal mucosa, colorectal mucosa, pancreatic duct epithelium and liver duct epithelium preneoplastic/neoplastic diseases.
8. The method according to claim 1 wherein a sample of said vertebrate is assayed to detect therein or to detect and quantitate therein MN antigen or MN nucleic acid.
9. The method according to claim 8 wherein said sample is selected from the group consisting of tissue sections, tissue extracts, tissue smears, whole cells, cell lysates, exfoliated cells, cell extracts, and body fluids.
10. The method according to claim 9 wherein said body fluids are selected from the group consisting of blood, serum, plasma, urine, semen, breast exudate, saliva, sputum, tears, mucous, fecal suspensions, gastric secretions, bile, lymph, cytosols, ascites, pleural effusions, amniotic fluid, bladder washes, bronchioalveolar lavages and cerebrospinal fluid.
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