WO2006057623A1

WO2006057623A1 - Runx3 antibodies and method of obtaining the antibodies

Info

Publication number: WO2006057623A1
Application number: PCT/SG2005/000394
Authority: WO
Inventors: Yoshiaki Ito; Kosei Ito
Original assignee: National University Of Singapore
Priority date: 2004-11-29
Filing date: 2005-11-18
Publication date: 2006-06-01

Abstract

The present invention relates to antibodies for specifically detecting RUNX3. In particular, to the antibody DSM ACC2673. Accordingly, the present invention also relates to a method for obtaining the antibodies. The present invention also relates to diagnostic methods for the detection of expression of RUNX3.

Description

RUNX3 Antibodies and Method of obtaining the antibodies

Field of the invention

The present invention relates to antibodies specific for RUNX3 and to methods for preparing the antibodies. Further, the invention relates to diagnostic methods for the detection of the expression of RUNX3.

Background of the invention

Gastric cancer is the second leading cause of cancer death worldwide. However, the molecular mechanism of carcinogenesis is not well known and there are no reliable molecular markers for the detection of gastric cancer. Gastric cancer traditionally carries a poor prognosis with 79% of tumours diagnosed at stage IV and five year survival less than 5%. Advanced gastric cancer is generally refractory to chemotherapy, which leads to poor prognosis. It has been shown that if it is diagnosed at an early stage, it is a curable disease.

Cadherine and several other genes are known to be involved in a certain percentage of gastric cancer. However, this percentage is relatively small. In a recent report, it was found that RUNX3 is a major tumour suppresser of gastric cancer. In fact, RUNX3 is involved in 40% of stage 1 gastric cancer and over 90% of stage 4 gastric cancer. The RUNX3 gene was characterised, as described in WO 02/061069 (herein incorporated by reference). WO 02/061069 also mentions a microchip for the diagnosis of cancers, using parts of the RUNX3 cDNA or an antibody against a RUNX3 protein produced from the cDNA. However, there is no method is described or any suggestion given in the specification that would enable a person skilled in the art to either prepare the antibodies or the microchip. Further, the specification also does not give any indication as to which part of the cDNA of the RUNX3 gene should be used for the production of antibodies against RUNX3.

Another publication [Levanon et. al., Mech. Of Dev., 2001 , 109:413-417] discloses a polyclonal anti-RUNX3 rabbit antibody. However, the antibody disclosed in that publication is a pan-reactive antibody. It reacts with both RUNX1 and RUNX 3 and is therefore not an antibody specific to RUNX3.

For the above stated reasons, there is still a need in the art for an antibody specific to RUNX3. Detection of the loss of RUNX3 expression would enable the early diagnosis of gastric cancer.

Summary of the invention

The present invention addresses the problems above, and in particular provides isolated nucleic acids, polypeptides, antibodies specific for RUNX3, and method for the detection of the expression of RUNX3.

According to one aspect, the invention provides an isolated nucleic acid selected from the group consisting of:

(a) nucleic acid comprising the polynucleotide of SEQ ID NO:2;

(b) nucleic acid comprising the polynucleotide encoding a polypeptide of SEQ ID NO:3;

(c) nucleic acid comprising the polynucleotide of SEQ ID NO:4;

(d) nucleic acid comprising the polynucleotide encoding a polypeptide of SEQ ID NO:5; and

(e) nucleic acid which hybridises to a nucleic acid complementary to the nucleic acid of (a), (b), (c) and/or (d) or a fragment thereof, and wherein the nucleic acid expresses a RUNX3 polypeptide specifically recognised by or binds to the antibody of DSM ACC2673.

In particular, the polynucleotide of SEQ ID NO:2 or SEQ ID NO:4 is part of the RUNX3 gene.

The isolated nucleic acid is further comprised in a vector. In particular, the vector is an expression vector. The vector may be inserted into a host cell.

According to another aspect, a vector comprising the isolated nucleic acid of any aspect of the present invention is provided. The vector may be an expression vector.

According to another aspect, the nucleic acid encodes a polypeptide. In particular, the polypeptide has an amino acid sequence of SEQ ID NO:3 or SEQ ID NO:5, or a fragment thereof.

Another aspect of the present invention is a polypeptide or a fragment thereof, wherein the polypeptide or fragment thereof is encoded by any nucleic acid of the present invention. In particular, the polypeptide comprises the amino acid sequence of SEQ ID NO:3 or SEQ ID NO:5. The polypeptide is encoded by a nucleic acid comprising the polynucleotide of SEQ ID NO:2 or SEQ ID NO:4. The fragment of the polypeptide may be an immunogenic fragment.

According to another aspect, the present invention provides a host cell comprising: the isolated nucleic acid according to any aspect of the invention; or the vector according to any aspect of the present invention.

The present invention also provides a method for the preparation of a polypeptide or fragment thereof. The polypeptide, or fragment thereof, of the present invention may be obtained according to the method comprising the steps: - culturing a host cell, comprising the nucleic acid to express the polypeptide; and

- isolating the polypeptide.

Yet another aspect is a pharmaceutical composition, which comprises any polypeptide, or an immunogenic fragment thereof, of the present invention. The pharmaceutical composition may comprise at least one pharmaceutically acceptable excipient, vehicle, diluent and/or carrier.

According to another aspect, the present invention provides an isolated antibody which specifically binds to at least a polypeptide selected from the group consisting of:

(a) a polypeptide comprising the amino acid sequence of SEQ ID NO:3 or an immunogenic fragment thereof; and

(b) a polypeptide comprising the amino acid sequence of SEQ ID NO:5 or an immunogenic fragment thereof.

In particular, the antibody has the accession number of DSM ACC2673.

According to a further aspect, the antibody is a monoclonal, polyclonal, chimeric, humanised, single chain, Fab, Fab', F(ab)' fragments and/or F(v) portions of the whole antibody.

The present invention also provides a method for producing the monoclonal antibody comprising the steps:

- immunising an animal with a polypeptide comprising amino acid of SEQ ID NO:3 or SEQ ID NO:5, or an immunogenic fragment thereof;

- isolating antibody-producing cells from the animal; - fusing the antibody-producing cells with immortalised cells to form monoclonal antibody-producing hybridoma cells;

- culturing the hybridoma cells; and

- isolating from the culture a monoclonal antibody which specifically binds to a polypeptide comprising SEQ ID NO:3 or SEQ ID NO:5.

According to another aspect, the present invention also provides a method for producing the polyclonal antibody comprising the steps:

- immunising an animal with a polypeptide of SEQ ID NO: 3 or SEQ ID NO:5, or an immunogenic fragment thereof;

- isolating antibodies from said animal; and

- screening the isolated antibodies with the polypeptide, thereby identifying a polyclonal antibody which specifically binds to a polypeptide comprising the SEQ ID NO:3 or SEQ ID NO:5.

A further aspect is a composition comprising the antibody of any aspect of the present invention. The composition may further comprise an acceptable excipient, vehicle, diluent and/or carrier.

Another aspect of the present invention is an antibody fixed on an insoluble support, preferably a solid support. The support may be used as a component, which may be part of a diagnostic kit. Alternatively, the diagnostic kit may comprise the antibody of the present invention in any other form.

The present invention also provides a diagnostic method for the detection of expression of gene for RUNX3 in a biological sample. The method comprises the steps of:

- obtaining the biological sample; - contacting the biological sample with an antibody of the present invention to form an antibody: polypeptide complex; and

- detecting the complex, wherein the presence of the complex correlates with the presence of the polypeptide in the biological sample.

The method can be used for the detection of cancer, in particular, gastric cancer. Also, as a further aspect, the antibody may be fixed on an insoluble support, preferably a solid support.

The invention also provides a diagnostic kit comprising a polypeptide according to any embodiment of the invention and/or the antibody of the invention. The polypeptide and/or antibody may be free is solution or fixed on a support, as explained above. The kit may further comprise information on use of the kit and/or antibody.

Brief description of the figures

Figure 1 : Purity and size of purified polypeptide as an antigen. 13.5 kDa polypeptide was visualised by Coomassie blue staining on 12% SDS-polyacrylamide gel.

Figure 2: Specificity of 6E9 against RUNX3 and Runx3. (A) Immunodetection of human RUNX1 (lane 1), human RUNX2 (lane 2), human RUNX3 (lane 3), murine Runxi (lane 4), murine

Runx2 (lane 5), and murine Runx3 (laneθ) expressed in COS7 cells by 0.1 μg/ml of 3D9, a purified anti-Runt domain monoclonal antibody (pan-reactive anti-RUNX antibody) by Western blotting. (B) Immunodetection of human RUNX and murine Runx proteins by 200 fold-diluted supernatant of 6E9 culture. (C) Immunodetection of human RUNX and murine Runx proteins by 40,000 fold-diluted purified polyclonal antibody reported by Levanon et al., Mech. OfDev., 2001 , 109:413-417.

Figure 3: Mapping of 6E9 binding site (epitope) on RUNX3. (A) Immunodetection of Flag-tagged full-length RUNX3 (lane 1 ) and Flag-tagged truncated forms of RUNX3 (lane 2: amino acids 1-

373; lane 3: amino acids 1-325; lane 4: amino acids 1-283; lane 5: amino acids 1-234; lane 6: amino acids 1-187) by 0.2 μg/ml of anti-Flag monoclonal antibody. (B) Immunodetection of Flag- tagged full-length RUNX3 and Flag-tagged truncated forms of RUNX3 by 200 fold-diluted supernatant of 6E9 culture.

Figure 4: Immunodetection of RUNX3 on gastric epithelial cells by 6E9. (A) Normal gastric epithelium from human gastric body stained by 6E9. Chief cells and surface epithelial cells express RUNX3 strongly. Counter staining done by hematoxyline. Scale bar is equal to 500μm. (B) Expression of RUNX3 in surface epithelial cells. Enlargement of the upper boxed region in (C). Arrow heads show expression of RUNX3 in lymphocytes. Scale bar is equal to 50μm.

Brief Description of Sequence Listings

SEQ ID NO:1 is the nucleotide sequence of human RUNX3 cDNA disclosed in WO 02/061069 (nucleotides 1 to 1320)(herein incorporated by reference)

SEQ ID NO:2 is a part of SEQ ID NO:1.It comprises nucleotides 577 to 909 of the human RUNX3 cDNA, which encodes the antigen for the purposes of the present invention.

SEQ ID NO:3 is the polypeptide encoded by SEQ ID NO:2. SEQ ID NO:4 is a part of SEQ ID NO:1 and of SEQ ID NO:2, in particular, it comprises nucleotides 577 to 711 of the human RUNX3 cDNA, containing the sequence corresponding to the epitope.

SEQ ID NO:5 is the polypeptide encoded by SEQ ID NO:4, comprising the epitope.

SEQ ID NO: 6 is the flag-tagged sequence.

SEQ ID NO:7 is a primer used for the amplification of the middle 1/3 fragment.

SEQ ID NO:8 is a primer used for the amplification of the middle 1/3 fragment.

Detailed description of the invention

The present invention provides antibodies specific for RUNX3 gene and a method for the detection of the loss of expression of RUNX3.

Gastric carconimas have been linked with the loss of homozygosity at various chromosomal loci, but no single gene that accounts for the majority of cases has been identified. However, it was reported [Li et al., Ce//, 2002, 109:113- 124] that the gastric mucosa of Runx3 null mice showed hyperplasia and concluded that lack of RUNX3 is causally related to human gastric cancer.

RUNX3, the third ranf-related gene, is expressed in the glandular stomach epithelial cells, and Runx3 null gastric mucosa develops hyperplasias due to promotion of proliferation and suppression of apoptosis in epithelial cells.

An analysis of RUNX3 in human stomach cancer cell lines and primary human tumours revealed hemizygosity in 30% of the tumours analysed, and silencing of the tumours analysed RUNX3 is silenced in gastric cancer by hypermethylation of CpG islands in the exon 1 region. It would therefore be useful to detect a loss of expression of RUNX3 gene for the early diagnosis of cancer. This can be done so with the aid of antibodies to detect the presence of RUNX3.

Accordingly, the first aspect of the present invention provides an isolated nucleic acid selected from the group consisting of:

(a) nucleic acid comprising the polynucleotide of SEQ ID NO:2;

(b) nucleic acid comprising a polynucleotide encoding the polypeptide of SEQ ID NO:3;

(c) nucleic acid comprising the polynucleotide of SEQ ID NO:4;

(d) nucleic acid comprising a polynucleotide encoding the polypeptide of SEQ ID NO:5; and

(e) nucleic acid which hybridises to a nucleic acid complementary to the nucleic acid of (a), (b), (c) or (d), or a fragment thereof, and wherein the nucleic acid expresses a RUNX3 polypeptide specifically recognised by or binds to the antibody of DSM ACC2673.

The antibody with accession number DSM ACC2673 was deposited with Deutsche Sammlung von Mikroorganismen Und Zellkulturen GmbH (DSMZ) on 5 August 2004.

The isolated nucleic acids of (a), (b), (c) and (d) refer not only to polynucleotides exactly as listed in SEQ ID NO:2 and SEQ ID NO:4, or polynucleotides encoding polypeptides of SEQ ID NO:3 and SEQ ID NO:5, but also the polynucleotides with additional nucleotides at the head and/or tail.

Nucleic acid as used herein refers to an oligonucleotide, nucleotide, or polynucleotide, and to cDNA, DNA, mRNA or RNA of genomic or synthetic origin which may be single- or double-stranded. Single-stranded DNA or RNA may be the coding strand, also known as the sense strand, or it may be the non-coding strand, also referred to as the antisense strand. Nucleic acid also includes nucleic acid molecules.

Isolated nucleic acid refers to a nucleic acid molecule, DNA or RNA, which has been removed from its natural environment. For example, recombinant

DNA molecules contained in a vector are considered isolated for the purposes of the present invention. Further examples of isolated DNA molecules include recombinant DNA molecules maintained in heterologous host cells, and those

DNA molecules purified (partially or substantially) from a solution whether produced by recombinant DNA or synthetic chemistry techniques. Isolated

RNA molecules include in vivo or in vitro RNA transcripts of the DNA molecules of the present invention.

Accordingly, the nucleic acid of SEQ ID NO:2 and SEQ ID NO:4 belong to a part of the human RUNX3 cDNA, which was disclosed in WO 02/061069 (herein incorporated by reference). In particular, the human RUNX3 cDNA described in SEQ ID NO:1 may be divided into three fragments, the N- terminus 1/3, middle 1/3 and C-terminus 1/3 fragments. The fragment used for the present invention is the middle 1/3 fragment of the cDNA. This was achieved by amplifying the middle 1/3 fragment (SEQ ID NO:2) of the cDNA according to any standard amplifying technique known in the art (see for example, Sambrook and Russell, Molecular Cloning, a Laboratory Manual, Cold Spring Harbour Laboratory Press, 2001 ). For example, PCR could be used for amplification, as seen in Example 1.

However, it should be noted that any known method known in the art can be used to obtain the middle 1/3 fragment from the RUNX3 DNA.

With reference to the nucleic acid (e), a nucleic acid is "hybridisable" to another nucleic acid (in the present case, a nucleic acid complementary to the nucleic acid of (a), (b), (c) or (d) or a fragment thereof), when a single- stranded form of the nucleic acid can anneal to the other nucleic acid under appropriate conditions of temperature and solution ionic strength (Sambrook and Russell, Molecular Cloning, A Laboratory Manual, Cold Spring Harbour Laboratory Press, 2001 ). The conditions of temperature and ionic strength determine the "stringency" of the hybridisation. Hybridisation requires the two nucleic acids to contain complementary sequences. Depending on the stringency of the hybridisation, mismatches between bases are possible. The appropriate stringency for hybridising nucleic acids depends on the length of the nucleic acids and the degree of complementation, variables well known in the art. The greater the degree of similarity or homology between two nucleotide sequences, the greater the value of Tm for hybrids of nucleic acids having those sequences. The relative stability (corresponding to higher Tm) of nucleic acid hybridisation decreases in the following order: RNA: RNA, DNA:RNA, DNA:DNA. For hybrids of greater than 100 nucleotides in length, equations for calculating Tm have been derived (Sambrook and Russell, 2001 , as above). For hybridisation with shorter nucleic acids, i.e. oligonucleotides, the position of mismatches becomes more important, and the length of the oligonucleotide determines its specificity (Sambrook and Russell, 2001 , as above). Preferably a minimum length for a hybridisable nucleic acid is at least about 10 nucleotides; more preferably at least about 15 nucleotides; most preferably the length is at least about 18 nucleotides.

The invention also provides a vector comprising at least one of the nucleic acids (a), (b), (c), (d) or (e). For example, the vector may comprise or be a bare nucleic acid segment, a plasmid, a phage, a virus, a viroid or a transposable element. The vector may further comprise a regulatory nucleic acid sequence linked to the nucleic acid encoding the polypeptide. The regulatory nucleic acid may be a prokaryotic or eukaryotic promoter.

The polynucleotides of the present invention may be joined to a vector containing a selectable marker for propagation in a host. Generally, a plasmid vector is introduced into mammalian or avian cells in a precipitate, such as a calcium phosphate precipitate, or in a complex with a charged lipid (e.g., LIPOFECTAMINE.TM.; Life Technologies, Inc.; Rockville, Md.) or in a complex with a virus (such as an adenovirus; see U.S. Pat. Nos. 5,547,932 and 5,521 ,291) or components of a virus (such as viral capsid peptides). If the vector is a virus, it may be packaged in vitro using an appropriate packaging cell line and then transduced into host cells. These host cells can be prokaryotic or eukaryotic host cells.

The expression vectors will preferably include at least one selectable marker. Such markers include, but are not limited to, dihydrofolate reductase (dhfr) or neomycin (neo) resistance for eukaryotic cell culture and tetracycline (tet) or ampicillin (amp) resistance genes for culturing in E. CoIi and other bacteria.

Representative examples of appropriate hosts include, but are not limited to, bacterial cells, such as Escherichia spp. cells (particularly E. coli), Bacillus spp. cells particularly B. cereus, B. subtilis and B. megaterium), Streptomyces spp. cells, Salmonella spp. cells (particularly S. typhimurium) and Xanthomonas spp. cells; fungal cells, including yeast cells such as Saccharomyces spp. cells; insect cells such as Drosophila S2, Spodoptera Sf9 or Sf2l cells and Trichoplusa High-Five cells; other animal cells particularly mammalian cells and most particularly human cells such as CHO, COS, VERO, HeLa, myeloma cells, Bowes melanoma cells and HepG2 and other liver cell lines; and higher plant cells. Appropriate culture media and conditions for the above-described host cells are known in the art.

Among vectors preferred for use in bacteria include pQE70, pQE6 and pQE-9, available from Qiagen; pBS vectors, Phagescript vectors, Bluescript vectors, pNH8A, pNH16a, pNH18A and pNH46A, available from Stratagene; pcDNA3 available from Invitrogen; and pGEX, pTrxfus, pTrc99a, pET-5, pET-9, pKK223-3, pKK233-3. pDR540 and pRIT5 available from Pharmacia. Among preferred eukaryotic vectors are pWLNEO, pSV2CAT, pOG44, pXT1 , pBK and pSG available from Stratagene; and pSVK3, pBPV, pMSG and pSVL available from Pharmacia. Other suitable vectors will be readily apparent to the skilled artisan.

In the present invention, pQE-9 bacterial expression vector was inserted into SG13009 (pREP4) cells, a strain of E. CoIi. This is further described in Example 1 below.

Introduction of the vector into the host cell can be effected by various methods, which are described in many standard laboratory manuals, such as (Sambrook and Russell, 2001 , as above).

According to another aspect, the present invention provides an isolated polypeptide. The polypeptide may be encoded by any of the nucleic acids of the present invention, in particular, nucleic acid of SEQ ID NO:2 or SEQ ID NO:4. In particular, the polypeptide has an amino acid sequence of SEQ ID NO:3 or SEQ ID NO:5, or a fragment thereof. The polypeptide of the invention may comprise at least one of the amino acid sequences of SEQ ID NO:3 and SEQ ID NO:5.

The polypeptide of the invention may also be a fused peptide and comprise at least one polypeptide having the sequence of SEQ ID NO:3 or SEQ ID NO:5.

The polypeptide of the invention may be isolated and/or purified from biological material, expressed from recombinant DNA, and/or prepared by chemical synthesis. In particular, the polypeptide may be made according to the method comprising the steps:

- culturing a host cell, comprising the nucleic acid to express the polypeptide; and

- isolating the polypeptide. The host cell may be any suitable host cell as described above. In particular, the nucleic acid that expresses the polypeptide may be inserted into a vector, as described above, followed by introducing the vector into any suitable host cell. As an example (Example 1), which is intended to be non-limiting of the present invention, the isolated polynucleotide of SEQ ID NO:2 was inserted into pQE-9 bacterial expression vector (QIAGEN), which was then introduced into SG13009 (pREP4) cells, a strain of E. CoIi. The cells expressed the polypeptide of SEQ ID NO:3 and these were isolated and purified using QIAexpressionist (QIAGEN).

According to another aspect, the invention provides a pharmaceutical composition which comprises any polypeptide of the present invention. In particular, the composition comprises polypeptide of SEQ ID NO:3 or SEQ ID NO:5. The pharmaceutical preparation optionally comprises a pharmaceutically acceptable carrier, diluent, excipient or a combination thereof. The invention encompasses the preparation and use of pharmaceutical compositions comprising the polypeptide of the invention as an active ingredient. Such a pharmaceutical composition may consist of the active ingredient alone, in a form suitable for administration to a subject, or alternatively the pharmaceutical composition may comprise the active ingredient and one or more pharmaceutically acceptable carrier, excipient and/or diluent.

The pharmaceutical preparation may be in the form of oral, parenteral, injection, topical, and/or implant preparation.

Pharmaceutical compositions of polypeptides or fragments may be prepared. The composition may be used in therapeutic methods. For example, the composition may be used for inducing further antibodies.

Compositions of the invention are provided to an animal by any suitable means, directly (e.g., locally, as by injection, implantation or topical administration to a tissue locus) or systemically (e.g., parenterally or orally). Where the compositions of the invention are to be provided parenterally, such as by intravenous, subcutaneous, opthalmic, intraperitoneal, intramuscular, buccal, rectal, vaginal, intraorbital, intracerebral, intracranial, intraspinal, intraventricular, intrathecal, intracistemal, intracapsular, intranasal or by aerosol administration, the composition preferably comprises part of an aqueous or physiologically compatible fluid suspension or solution.

According to yet another aspect, the present invention provides an isolated antibody which specifically binds to a polypeptide selected from a group consisting of:

(a) a polypeptide comprising the amino acid of SEQ ID NO:3 or an immunogenic fragment thereof; and

(b) a polypeptide comprising the amino acid of SEQ ID NO:5 or an immunogenic fragment thereof.

In particular, the antibody of the present invention has an accession number of DSM ACC2673.

According to the invention, the polypeptide of any aspect of the invention or immunogenic fragments thereof may be used as an immunogen to generate antibodies that recognise the polypeptides of the invention.

An antibody is any immunoglobulin, including antibodies and fragments thereof, that bind to a specific epitope. The antibody according to the invention may be prepared against a polypeptide having the amino acid sequence of at least one of SEQ ID NOS:3 or 5 or a fragment thereof. Such antibodies include, but are not limited to polyclonal, monoclonal, chimeric, humanised, single chain, Fab, Fab', F(ab)' fragments and/or F(v) portions of the whole antibody. Various procedures known in the art may be used for the production of polyclonal antibodies to the polypeptide of the invention, or immunogenic fragment thereof. For the production of antibody, various host animals can be immunised by injecting the polypeptide or an immunogenic fragment thereof, including but not limited to rabbits, mice, rats, sheep, goats, etc. In one embodiment, the peptide of the invention or fragment thereof can be conjugated to an immunogenic carrier, e.g., bovine serum albumin (BSA) or keyhole limpet hemocyanin (KLH). The peptide of the invention or immunogenic fragment may be further combined with any adjuvant known in the art (for example, Hood et al., in Immunology, p. 384, Second Ed., Benjamin/Cummings, Menlo Park, Calif., 1984, herein incorporated by reference).

In particular, the polyclonal antibody is produced by a method comprising the steps:

- immunising an animal with a polypeptide of SEQ ID NO:3 or SEQ ID NO:5, or an immunogenic fragment thereof;

- isolating antibodies from said animal; and

For the preparation of monoclonal antibodies directed towards the polypeptide of the invention or immunogenic fragment thereof, any technique that provides for the production of antibody molecules by continuous cell lines in culture may be used. These include, but are not limited to, the hybridoma technique originally developed by Kohler et al., Nature, 256:495-497 (1975), as well as the trioma technique, the human B-cell hybridoma technique (Kozbor et al., Immunology Today, 4:72, 1983), and the EBV-hybridoma technique to produce human monoclonal antibodies (Cole et al., in Monoclonal Antibodies and Cancer Therapy, pp. 77-96, Alan R. Liss, Inc., 1985). Immortal, antibody- producing cell lines can be created by techniques other than fusion, such as direct transformation of B lymphocytes with oncogenic DNA, or transfection with Epstein-Barr virus, e.g., M. Schreier et al., "Hybridoma Techniques" (1980); Hammerling et al., "Monoclonal Antibodies And T-cell Hybridomas" (1981); Kennett et al., "Monoclonal Antibodies" (1980); also US 4,341 ,761 ; US 4,399,121 ; US 4,427,783; US 4,444,887; US 4,451 ,570; US 4,466,917; US 4,472,500; US 4,491 ,632; or US 4,493,890.

In particular, the monoclonal antibody can be produced according to the method comprising the steps:

- isolating antibody-producing cells with immortalised cells to form monoclonal antibody-producing hybridoma cells;

- culturing the hybridoma cells; and

An example of the method used for the production of the antibody of the present invention is given in Example 1. Example 1 provides a method used for the production of monoclonal antibody DSM ACC2673 using BALB/c mice.

In addition, techniques developed for the production of "chimeric antibodies" (Morrison, et al., 1984, Proc. Natl. Acad. Sci., 81 ,6851-6855; Neuberger, et al., 1984, Nature 312,604-608; Takeda, et al., 1985, Nature, 314,452-454, incorporated herein by reference in their entirety) by splicing the genes from a mouse antibody molecule of appropriate antigen specificity together with genes from a human antibody molecule of appropriate biological activity can be used. For example, the genes from a mouse antibody molecule specific for an autoinducer can be spliced together with genes from a human antibody molecule of appropriate biological activity. A chimeric antibody is a molecule in which different portions are derived from different animal species, such as those having a variable region derived from a murine mAb and a human immunoglobulin constant region (See, e.g., Cabilly et al., US 4,816,567; and Boss et al., US 4,816,397, which are incorporated herein by reference in their entirety).

In addition, techniques have been developed for the production of humanized antibodies (See, e.g., Queen, US 5,585,089 and Winter, US 5,225,539, which are incorporated herein by reference in their entirety). An immunoglobulin light or heavy chain variable region consists of a "framework" region interrupted by three hypervariable regions, referred to as complementarity determining regions (CDRs). The extent of the framework region and CDRs have been precisely defined (see, "Sequences of Proteins of Immunological Interest", Kabat, E. et al., U.S. Department of Health and Human Services (1983), incorporated herein by reference in their entirety). Briefly, humanized antibodies are antibody molecules from non-human species having one or more CDRs from the non-human species and a framework region from a human immunoglobulin molecule.

Alternatively, techniques described for the production of single chain antibodies (US 4,946,778; Bird, 1988, Science 242, 423-426; Huston, et al., 1988, Proc. Natl. Acad. Sci. USA 85, 5879-5883; and Ward, et al., 1989, Nature 334, 544-546, incorporated herein by reference in their entirety) can be adapted to produce single chain antibodies against an immunogenic conjugate of the present invention. Single chain antibodies are formed by linking the heavy and light chain fragments of the Fv region via an amino acid bridge, resulting in a single chain polypeptide. Fab and F(ab')2 portions of antibody molecules may be f epared by the proteolytic reaction of papain and pepsin, respectively, on substantially intact antibody molecules by methods that are well-known. See for example, U.S. 4,342,566. Fab¹ antibody molecule portions are also well-known and are produced from F(ab')2 portions followed by reduction of the disulfide bonds linking the two heavy chain portions as with mercaptoethanol, and followed by alkylation of the resulting protein mercaptan with a reagent such as iodoacetamide.

In the production of antibodies, screening for the desired antibody can be accomplished by techniques known in the art, e.g., radioimmunoassay, ELISA (enzyme-linked immunosorbent assay), "sandwich" immunoassays, immunoradiometric assays, gel diffusion precipitin reactions, immunodiffision assays, in situ immunoassays (using colloidal gold, enzyme or radioisotope labels, for example), Western blots, precipitation reactions, agglutination assays (e.g., gel agglutination assays, hemagglutination assays), complement fixation assays, immunofluorescence assays, protein A assays, and immunoelectrophoresis assays, etc. In one embodiment, antibody binding is detected by detecting a label on the primary antibody. In another embodiment, the primary antibody is detected by detecting the binding of a secondary antibody or reagent to the primary antibody. In a further embodiment, the secondary antibody is labelled. Many means are known in the art for detecting the binding in an immunoassay and are within the scope of the present invention. For example, to select antibodies which recognize a specific epitope of a polypeptide of the invention (for example, any one of SEQ ID NOS:3 or 5), one may assay generated hybridomas for a product which binds to a polypeptide fragment containing such an epitope. For selection of an antibody specific to a polypeptide according to the invention from a particular species of animal, one can select on the basis of positive binding with the polypeptide of the invention expressed by or isolated from cells of that species of animal. According to a particular aspect, several cycles of cloning and re-cloning of hybridomas were carried out to obtain cells which produced anti-RUNX3 antibodies and showed no reactivity to RUNX1 and RUNX2. The screening of isolated antibodies was carried out by Western blotting method using anti- mouse immunoglobulin (Ig), HRP-linked whole antibody (Amersham; NA931V) as a second antibody and ECL Western blotting reagents (Amersham; RPN2106) were used for the detection of HRP activities.

Accordingly, 66 anti-RUNX3 producing clones were obtained, although Western blotting screened out only 8 clones. These 8 clones secreted anti- RUNX3 IgGI with high titers. However, only the antibody produced from one clone, referred to as 6E9, DSM ACC2673, was able to detect RUNX3 on the histological sections of human tissues by immunohistochemistry (Example 3). The overall method for obtaining the antibody of the present invention is described in greater detail in Example 1 below.

The specificity of the anti-RUNX3 monoclonal antibody obtained was compared to other RUNX antibodies. In particular, as described in Example 2, the 6E9 clone, DSM ACC2673, was compared with the antibody obtained from Levanon's group. From the results obtained, as shown in Figure 2, it could be seen that the antibody of the present invention specifically bound to RUNX3 only, whereas the other antibodies were pan-reactive and bound to RUNX1 , RUNX2 and/or RUNX3. Accordingly, the antibody from Levanon's group was not able to specifically bind to RUNX3.

The terms "specific binding" or "specifically binding", refers to that interaction between a protein or polypeptide and an agonist, an antibody and an antagonist. The interaction is dependent upon the presence of a particular structure (i.e., the antigenic determinant or epitope) of the protein recognized by the binding molecule. According to another aspect, the invention provides a composition comprising the antibody of any aspect of the present invention. The composition may further comprise an acceptable excipient, vehicle, diluent and/or carrier.

Another aspect of the present invention is to fix the antibody on a solid support, such as a microarray or biochip. The solid support may be used as a component of a diagnostic kit. The antibodies produced as described above may be covalently or non-covalently immobilized onto a solid support. A solid support may include any solid support to which an antibody can be immobilized, including but not limited to nitrocellulose, diazocellulose, glass, polystyrene, polyvinylchloride, polypropylene, polyethylene, dextran Sepharose, agar, starch, nylon, beads (including glass, latex, magnetic (including paramagnetic and superparamagetic) beads) and microtitre plates. Linkage of the antibodies of the invention to a solid support can be accomplished by attaching one or more ends of the antibody to the support. Attachment may also be made at one or more internal sites in the antibody. Multiple attachments (both internal and at the ends of the antibody) may also be used according to the invention. Attachment can be via an amino acid linkage group such as a primary amino group, a carboxyl group, or a sulfhydryl (SH) group or by chemical linkage groups such as with cyanogen bromide (CNBr) linkage through a spacer. For non-covalent attachments, addition of an affinity tag sequence to the antibody can be used such as GST (Smith, D. B., and Johnson, K. S. Gene 67:31 (1988)); polyhistidines (Hochuli, E. et al., J. Chromatog. 411 :77 (1987)); or biotin. Alternatively, an indirect coupling agent such as Protein A or Protein G (available commercially, e.g., from Sigma Chemical Co, St. Louis, Mo.) which binds to the Fc region of antibodies may be attached to the solid support and the antibodies of the invention attached thereto, by simply incubating the antibodies with the solid support containing the immobilized Protein A or Protein G. Such affinity tags may also be used for the reversible attachment of the antibodies of the present invention to the support.

According to yet another aspect of the present invention is a kit, in particular a diagnostic kit. The diagnostic kit may comprise the antibody of any aspect of the invention. Accordingly, the kit may comprise the antibody of the present invention fixed onto an insoluble support, for example a solid support. The diagnostic kit may also comprise the antibody in the form of frozen or lyophilized (freeze-drying) antibodies, or antibody fragments to be reconstituted, respectively, by thawing (optionally followed by further dilution) or by suspension in a (preferably buffered) liquid vehicle. The kits may also include buffer and/or excipient solutions (in liquid or frozen form), or buffer and/or excipient powder preparations to be reconstituted with water, for the purpose of mixing with the antibodies for use for diagnosis purposes. Preferably, the kit may also comprise instructions for reconstituting and using the antibodies for the detection of diseases, for example, for the detection of cancer. In particular, for the detection of gastric cancer. The buffers, excipients and other component parts can be sold separately or together with the kit.

Accordingly, the present invention provides a diagnostic method for the detection of expression of gene for RUNX3 in a biological sample. The method comprises the steps:

- obtaining the biological sample;

- contacting the biological sample with an antibody of the present invention to form an antibody:polypeptide complex; and

- detecting the complex, wherein the presence of the complex correlates with the presence of the polypeptide in the biological sample. The method can be used for the detection of cancer, in particular, gastric cancer.

As mentioned above, RUNX3 is a tumour suppressing gene. The RUNX3 gene will not be expressed in a person suffering from cancer. It would therefore be advantageous to use the antibody of the present invention for the early detection of cancer. For example, a biological sample is obtained from a human, and that sample is tested against the antibody of the present invention according to the diagnostic method described above. If it is found that the antibody does not bind to any epitope, it shows that RUNX3 is not present, indicating that the human is suffering from gastric cancer.

As the antibody of the present invention is specific to RUNX3, it would make diagnosis a lot easier and faster, as can be seen from the above illustration.

Having now generally described the invention, the same will be more readily understood through reference to the following examples, which are provided by way of illustration and are not intended to be limiting of the present invention.

EXAMPLES

Standard molecular biology techniques known in the art and not specifically described were generally followed as described in Sambrook and Russel, Molecular Cloning: A Laboratory Manual, Cold Springs Harbor Laboratory, New York (2001 ).

Example 1

Obtaining the RUNX3 cDNA fragment

The human RUNX3 cDNA of SEQ ID NO:1 (Locus NM_004350, as obtained from the NCBI Nucleotide Database) was used. Based on the human RUNX3 cDNA, the middle 1/3 fragment of SEQ ID NO:2 was amplified by the PCR method. The primers were constructed on the basis of the known sequence flanking the middle 1/3 fragment according to standard technique well-known in the art (see for example, Sambrook and Russel, 2001). The nucleotide sequence of the middle 1/3 fragment (SEQ ID NO:2) corresponds to RUNX3 nucleotides from nucleotides 577 to 909. The primers used for the amplification are as follows:

Primer 1 : 5'-AAgCTggAgCTgCAgACCAAgCCg-3' (SEQ ID NO:7)

Primer 2: 5'-TATggTggAAgCTTCTggTggTggCCg-3' (SEQ ID NO:8)

Expression and purification of polypeptide ofRUNX3 as an antigen

The QIAexpressionist (QIAGEN) kit, a kit based on E. CoIi expression system was used for the expression and purification of the polypeptide corresponding to the polynucleotide of SEQ ID NO:2.

The middle 1/3 fragment of human RUNX3 comprising of RUNX3 nucleotides from 577 to 909 (SEQ ID NO:2) was inserted between Bam HI and Hind III sites of pQE-9 bacterial expression vector. The vector, pQE9, has 6 times repeats of His encoding sequences. The vector was constructed in such a way that the translation started from the 6xHis tag sequence and continued to the middle 1/3 fragment of cDNA inserted (i.e. the 6xHis Tag was already comprised in the vector pQE9). As a result, a 6xHis tagged recombinant polypeptide was produced. Further the vector was introduced into the host cell by the conventional heatshock method.

The 6xHis-tagged recombinant polypeptide was induced by 1 mM IPTG for 6 hours in SG13009 (pREP4) cells, a strain of E. CoIi supplied by Qiagen. The

E.Coli cells were then lysed under a denaturing condition using a 6M guanidine hydrochloride buffer (pH 8.0) and the lysate was applied onto Ni- NTA (n ickel-n itri lotriacetic acid) resins. After washing with 8M urea buffer (pH 6.3), the polypeptide was eluted from the resins using a 8M urea buffer of pH 4.5. The eluted polypeptide was dialyzed against 2M urea and 40% glycerol in PBS.

The purity of the polypeptide was checked on 12% SDS-polyacrylamide gel electrophoresis (SDS-PAGE) by Coomassie staining. The results obtained are shown in Figure 1. A total of 600 μg of purified polypeptide (1.5 mg/ml, 400 μl) was obtained.

This 6xHis-tagged polypeptide of SEQ ID NO:3, which consisted of 111 amino acids from the human RUNX3 protein (from amino acid 190 to 300) was to be used as the antigen for generating the antibodies.

Generation and screening of anti-RUNX3 monoclonal antibodies

The purified polypeptide of human RUNX3 (from amino acids 190 to 300) of SEQ ID NO:3 obtained from the previous step was used as the antigen for generating the antibodies and injected into 7 week old female BALB/c mice.

25 μg of the purified polypeptide in 0.1 ml PBS, which was emulsified with 0.1 ml Freund's complete adjuvant was injected subcutaneously per mouse. The day the polypeptide was injected into the mice was denoted as Day 0. Two mice were used. Subsequently, booster injections were given.

An intraperitoneal booster injection of 50 μg in 0.1 ml PBS with 0.1 ml incomplete adjuvant was given to each mouse on day 14. Alternatively, a subcutaneous booster injection of 12 μg polypeptide, in 0.1 ml PBS with 0.1 ml incomplete adjuvant was given to each mouse on day 60. On day 69, the mice were bled and the presence of antibodies against RUNX3 was examined by Western blotting. On day 70, the mice were boosted again by an intravenous injection of 12 μg polypeptide in 0.2 ml PBS per mouse.

On day 74, the spleens of the mice were removed from immunized mice and the splenocytes (lymphocytes) were fused with the SP2-K13 mouse myeloma cell line, a sub-clonal line from Sp2/0-Ag14 myeloma cells, according to the technique as described in Galfre et al., Nature, 1997, 266:550-552, using 50% PEG.

The limiting dilution technique with thymocyte feeder cells from BALB/c mice was used to clone individual hybridomas. The feeder cells support growth of isolated hybridoma cells until cell division of hybrid cells produce sufficient cell density. The high concentration of hybridoma cells were diluted with RPMI 1640 medium (GIBCO No. 11875) as the diluent, to obtain a diluted concentration of cells. The individual hybridoma cells were then placed in a 96-well plate.

The hybridoma culture fluids were screened for secreted antibodies against RUNX3 by Western blotting using the extract from COS7 cells exogenously expressing human full-length RUNX3. Anti-mouse immunoglobulin (Ig), HRP- linked whole antibody (Amersham; NA931V) was used as a second antibody and ECL Western blotting detection reagents (Amersham; RPN2106) were used to detect HRP activities. Three cycles of cloning and re-cloning to screen the hybridoma cells were performed to obtain the cells which secreted anti- RUNX3 antibodies and showed no reactivities to human RUNX1 and RUNX2. The method used to determine whether the antibodies tested showed reactivity towards RUNX1 , RUNX2 AND RUNX3 was Western Blotting. As shown in Figure 2B, on the membrane, all three RUNX proteins (both human and mouse) were present. However, the monoclonal antibody reacted only with RUNX3 of human and mouse origin. The types of immunoglobulin secreted from hybridomas were determined by a mouse monoclonal antibody isotyping kit (Amersham; RPN29) consisting of typing sticks which carried goat antibodies specific for different types of murine Ig peptide chains according to the protocol.

As a result, 66 anti-RUNX3 producing clones were obtained. However, only 8 clones, which secreted anti-RUNX3 IgGI antibodies with high titers, were finally screened out by Western blotting. Out of these 8 clones, the antibody produced from one clone, referred to as 6E9 (DSM ACC2673) was found to be the only one which could detect RUNX3 on the histological sections of human tissues by immunohistochemistry, as described in Example 3.

Characterization of anti-RUNX3 monoclonal antibody, 6E9

The epitope of RUNX3 for 6E9 was mapped on Western blotting. Extracts of COS7 cells which expressed Flag-tagged full-length RUNX3 or Flag-tagged truncated forms of RUNX3 (1-187 amino acids, 1-234 amino acids, 1-283 amino acids, 1-325 amino acids, and 1-373 amino acids) by pcDNA3 expression vectors (Hanai et al., J. Biol. Chem., 1999, 274:31577-3582; Guo et al., Oncogene, 2002, 21 :8351-8355) were used as antigens for the epitope mapping. The extracts were separated by 10% SDS-PAGE gels and subjected to Western blotting. Flag-tagged referred to a tag of sequence

DYKDDDDK.

The amounts of Flag-tagged full-length RUNX3 or Flag-tagged truncated forms of RUNX3 applied on the gels were visualized by anti-Flag monoclonal antibody (Sigma; M2 clone), results of which are shown in Figure 3A. 6E9 showed reactivity to all the truncated forms except for RUNX3 (amino acid 1 to 187), indicating that the epitope for 6E9 lies within amino acids 188 to 234 of RUNX3 (Figure 3B). The fragment of RUNX3 lacking the C-terminal portion from amino acid 188 did not react with 6E9, whereas the fragment lacking the C-terminal portion from amino acid 235 did. This means that the epitope which 6E9 recognises must be present within the region between amino acidi 88-234 of RUNX3 (Figure 3B). Since the antigen used to immunize mice was RUNX3 (amino acid 190 to amino acid 300, SEQ ID NO:3), the epitope was found to be present between amino acid 190 and amino acid 234, as indicated by SEQ ID NO:5.

Example 2

Characterization and comparison of anti-RUNX3 monoclonal antibody (6E9 clone) to other RUNX antibodies

The specificity of the 6E9 clone (DSM ACC2673) was tested. The results are shown in Figure 2.

Extracts of COS7 cells which exogenously express human full-length RUNX1 , RUNX2, RUNX3, murine full-length Runxi , Runx2 or Runx3 by pEF-Bos expression vectors (Zhang et al, 1997; Zhang et al, 2000; Bae et al, 1995; Bae et al, 1994; Ogawa et al, 1993; murine Runx3 cDNA, AF155880 was inserted into EcoRI sites of pEF-Bos vector) were used as test antigens for the examination of specificities of the antibodies on Western blotting. The extracts were separated by 10% SDS-PAGE and subjected to Western blotting.

The amounts of RUNX (Runx) proteins applied on the gels were normalised by Western blotting using an anti-Runt domain monoclonal antibody (3D9) which was isolated previously (Figure 2A). 1726-2112 bp of human RUNX1 cDNA (accession number NM_001001890) (50-178 amino acid; Runt domain of RUNX1) was amplified by PCR. This was 6xHis tagged and expressed in E. coli. The protein product was used as an antigen. Mouse monoclonal antibodies were made in the same way that the antibody 6E9 of the present invention was produced and screened by Western blotting. Although the antigen was derived from RUNX1 , the monoclonal antibody 3D9 was found to react with all three RUNX proteins, presumably because the Runt domains of the three RUNX proteins are highly homologous.

The RUNX (Runx) proteins were normalised so that all the three RUNX proteins could be detected. The normalisation was done by comparing the darkness of the bands. The cell extracts were applied to the gel in such a way that when the Western blotting was performed, the darkness of the bands representing RUNX1 , RUNX2 and RUNX3 became comparable.

The Runt domain is a highly conserved domain among 3 family genes and it is known (Y. Ito, Genes to Cells, 1999, 4:685-696) that 3D9 can react with them equally. 6E9 reacted only with RUNX3/Runx3, not with RUNX1/Runx1 or RUNX2/Runx2, as shown in Figure 2B. By comparing the reactivity against human RUNX3 and mouse Runx3, 6E9 was found to have a higher affinity to human RUNX3 than to murine Runx3 (Figure 2B).

It should be noted that RUNX3 refers to human gene while Runx3 refers to mice gene. Further, as used herein, RUNX3/Runx3 refers to human and mouse RUNX3, respectively. RUNX1/Runx1 and RUNX2/Runx2 shall be construed accordingly.

In addition to the above, an aliquot of a polyclonal anti-RUNX3 rabbit antibody as reported in Levanon et al., Mech. Of Dev., 2001 , 109:413-417 was used. The aliquot of the antibody was obtained from the group of Levanon. As shown in Figure 2C, this antibody from Levanon et al. reacted with RUNX3/Runx3 but it also reacted almost equally with RUNX2/Runx2 and to a lesser degree with RUNX1/Runx1. Therefore, this antibody was considered to be a "pan-reactive" anti-RUNX antibody for practical purposes, i.e. it is an antibody which binds to RUNX polypeptides in general, but not specifically to the RUNX3 polypeptide.

From the results shown in Figure 2, it was clear that 6E9 (DSM ACC2673) was specific to RUNX3 as opposed to the polyclonal antibody described by Levanon et al (2001).

Example 3

Use of 6E9 to detect RUNX3 on human tissue sections by immunohistochemical method

The 6E9 antibody was applied on histological sections of human gastric tissue samples obtained from the Department of Pathology, National University of Singapore. 10% formalin-fixed gastric tissue samples were embedded in paraffin and cut into 5 μm sections. The rehydrated sections were warmed in a target retrieval solution (DAKO; S1700) at 96°C for 40 minutes. 20 fold- diluted supernatant of 6E9 culture medium with a diluent solution (DAKO; S3022) was applied on the slides at 4°C over night after blocking with a serum-free blocking solution (DAKO; X0909). A peroxidase-DAB based detection system, EnVision÷ kit (DAKO; K4006) was used to detect the immunoreactivities of 6E9 on the respective sections.

As shown in Figure 4, gastric epithelial cells were stained specifically. In particular, chief cells and surface epithelial cells in human gastric epithelium were stained strongly. This observation is consistent with the expression of Runx3 RNA in chief cells and surface epithelial cells in murine gastric epithelium revealed by in situ hybridization using an antisense Runx3 RNA probe (Li et al., Ce//, 2002, 109:113-124). Subsequently, 6E9 producing cells were adapted to serum-free culture and 6E9 IgGI was purified. 0.1 μg/ml of purified 6E9 IgGI was found to be adequate to detect RUNX3 by the immunohistochemical method described in this example.

Claims

1. An isolated nucleic acid selected from the group consisting of:

(a) nucleic acid comprising the polynucleotide of SEQ ID NO:2;

(c) nucleic acid comprising the polynucleotide of SEQ ID NO:4;

(e) nucleic acid which hybridises to a nucleic acid complementary to the nucleic acid of (a), (b), (c) or (d) or a fragment thereof, wherein the nucleic acid expresses a RUNX3 polypeptide that specifically binds to antibody of DSM ACC2673.

2. The isolated nucleic acid according to claim 1 , wherein the nucleic acid of SEQ ID NO:2 or SEQ ID NO:4 is part of gene RUNX3.

3. A polypeptide or a fragment thereof, wherein the polypeptide or fragment thereof is encoded by any nucleic acid according to claim 1 or claim 2..

4. A polypeptide, wherein the polypeptide has the sequence of SEQ ID NO:3 or SEQ ID NO:5, or a fragment thereof.

5. The polypeptide or fragment thereof according to claim 3 or claim 4, wherein the fragment is an immunogenic fragment.

6. A vector comprising the isolated nucleic acid according to claim 1 or claim 2.

7. The vector according to claim 6, wherein the vector is an expression vector.

8. A host cell comprising: the isolated nucleic acid according to claim 1 or claim 2; or the vector according to claim 6 or claim 7.

9. The host cell according to claim 8, wherein the host cell is prokaryotic or eukaryotic.

10. The host cell according to claim 8 or claim 9, wherein the host cell is selected from a group consisting of mammalian cells, COS cells, myeloma cells, bacteria and yeast cells.

11. A method for the preparation of a polypeptide or fragment thereof, the method comprising the steps of:

- culturing a host cell, comprising the nucleic acid according to claim 1 or claim 2, or a vector according to claim 6 or claim 7, to express the polypeptide or fragment thereof; and

- isolating the polypeptide or fragment thereof.

12. The method according to claim 11 , wherein the fragment is an immunogenic fragment.

13. A pharmaceutical composition comprising the polypeptide or immunogenic fragment thereof according to any one of claims 3 to 5.

14. The pharmaceutical composition according to claim 13, further comprising at least one pharmaceutically acceptable excipient, vehicle, diluent and/or carrier.

15.An isolated antibody which specifically binds to a polypeptide selected from the group consisting of: (a) a polypeptide comprising the amino acid sequence of SEQ ID NO:3 or an immunogenic fragment thereof; and

16. The antibody according to claim 15, wherein the antibody is a monoclonal, polyclonal, chimeric, humanised, single chain, Fab, Fab', F(ab)' fragments and/or F(v) portions of the whole antibody.

17. The antibody according to claim 15 or claim 16, wherein the antibody has an accession number of DSM ACC2673.

18. The antibody according to claim 16 or claim 17, wherein the monoclonal antibody is produced by a method comprising the steps:

- isolating antibody-producing cells from the animal;

- fusing the antibody-producing cells with immortalised cells to form monoclonal antibody-producing hybridoma cells;

- culturing the hybridoma cells; and

19. The antibody according to claim 16 or claim 17, wherein the polyclonal antibody is produced by a method comprising the steps:

- immunising an animal with a polypeptide of SEQ ID NO:3 or SEQ ID NO:5, or an immunogenic fragment thereof; - isolating antibodies from said animal; and

20. The antibody according to any one of claims 15 to 19, wherein the antibody is fixed on a solid support.

21. A composition comprising the antibody according to any one of claims 15 to 19.

22. The composition according to claim 21 , wherein the composition further comprises an acceptable excipient, vehicle, diluent and/or carrier.

23. A diagnostic kit comprising the antibody according to any one of claims 15 to 20.

24. The diagnostic kit according to claim 23, wherein the diagnostic kit further comprises information on use of the kit and/or antibody.

25.A diagnostic method for detection of expression of gene for RUNX3 in a biological sample comprising the steps:

- obtaining the biological sample;

- contacting the biological sample with an antibody according to any one of claims 15 to 20 to form an antibody:polypeptide complex; and

26. The method of claim 25, wherein the method is for diagnosing cancer.

27. The method of claim 26, wherein the cancer is gastric cancer.

28. The method according to any one of claims 25 to 27, wherein the antibody is fixed on a solid support.