[Screening and preliminary analysis of colorectal carcinoma-associated antigen genes]

To screen and identify the genes coding for colorectal carcinoma-associated antigen and analyze the bioinformation of their cDNA sequences.

Immunoscreening of the cDNA phage-display library derived from human colorectal carcinoma was performed with autologous or allogeneic serum antibody from patients with colorectal cancer through SEREX approach. After amplification of the positive phage clones, the phage DNA was extracted and purified with Qiagen kit, and the fragment sizes of the cDNA of positive clones were identified by PCR and EcoR I and Hind III restriction endonucleases. The cDNAs of the positive clones were ligated into pUCm-T vector and sequenced. The bioinformation of cDNA sequences were analyzed against GenBank+EMBL+DDBJ+PDB Sequences Database.

Eleven positive clones were obtained after immunoscreening, and the sizes of the cDNA fragments were 1100, 1300, 1000, 2000, 1200, 1200, 700, 900, 600, 1200 and 1000 bp, respectively, representing 9 antigen genes, including 7 with homology with the known genes. Among the 11 obtained positive clones, 3 were the same cDNA having homology with interferon-induced transmembrance protein-1 and possessing anti-proliferation effect; another 6 represented different genes, namely human BAC clone RP11-453E17 whose function have not been cleared, human cartilage-hair hypoplasia region gene responsible for cartilage-hair hypoplasia, human chromosome 5 clone CTD-2030B15 with insertion mutation, human gene similar to anti tumor necrosis factor-alpha antibody light-chain Fab fragment associated with tumor growth, mRNA of human beta-2-microglobulin in relation to tumor cell proliferation, and human aldolase A gene promoting tumor cell proliferation. The other two cDNA sequences were not identified for homology with currently known genes in GenBank, and their functions awaits further investigation.