| The process of cancer consists of a series of sequential interrelated steps, each of which involves the action of a number of factors, such as genes, proteins and environmental factors etc. With the rapid development of molecular cancer biology, more and more molecular events are being understood. Investigating the relationship between those factors and discovering new target gene and target protein is likely to produce important significance for revealing the mechanisms of the process of cancer and supporting increasing evidence for early diagnosis and therapies even early cancer protections.Previously, we reported the identification of a novel gene SNC19 from a substractive cDNA library of normal intestinal mucosa, the expression of which was down-regulated in colorectal carcinoma by Zhejiang university cancer institute in the way of exploring new factors responsible for the progress of colorectal cancer. The study on the gene structure, chromosome assignment, RNA expression and its function showed that SNC19 genomic DNA had 50420 base pairs, comprised of 19 exons; Correspondingly its cDNA had 3142 base pairs , encoding 855 amino acids. The gene was assigned to human chromosome llq24-25. All works implicated that whatever mRNA or protein of SNC19 was expressed only in the epithelial derivedtissues and cell lines. In situ hybridization showed that the positive rate of SNC19 protein mRNA expressed in the mucosa adjacent to colotectal carcinoma of the lymphanode metastasis group (64.7%) was higher than that in non-metastasis goup(15.4%). The result had significant diffirence in statistics(P<0.05). Otherwise the encoding protein was predicted to be a type II membrane serine protease with a short cytoplasmic domain, a short transmembrane domain and a long extracellular domain of which C-terminal had serine proteolytic activity, suggesting that the protein may participate in the cell surface proteolysis, immediate cell functions even cancer invasion and metastasis.At the same time MT-SP1, which cDNA sequence was identical to that of SNC19., was cloned and characterized from the PC-3 human prostatic cancer cell line by Takeuchi group, and PAR2 (Protease-activated Receptor-2), sc-uPA (Single-chain Urokinase-type Plasminogen Activator) were identified as its substrates. In addition, there was another protein called matriptase which sequence appeared to be a partial SNC19 cDNA was reported by Lin.C.Y group. It was discovered in T-47D human breast cancer cells and was further purified from T-47D cell-conditioned medium and human milk with its partner HAI-1 and was proved to have the ability to activate pro-uPA and pro-HGF to their active forms in vitro. Epithin and XMT-SPI are the homologue genes of SNC19 in mouse and in Xenopus Laevis. uPA and HGF/SF have both emerged as important factors in degradation of ECM and cancer invasion, suggesting that SNC19/MT-SP1/matriptase may be a metastasis related gene and there may exist a complicated net including SNC19/MT-SP1 /matriptase and other proteinfactors to influence cancer invasion and metastasis. But more evidence was needed to support this viewpoint.To further investigate the relationship between SNC19 protein and cancer metastasis, it seemed very important to study the characteristics and function of this protein, so the institute produced monoclonal antibodies against SNC19 extracellular domain ( amino 565-855) and ZMG9 antibody was detected and selected. Based on the work as mentioned above, the dissertation was developed as follows:Part I. Differential expression and distribution of SNC19 protein in cancer cell lines and tissues.Western blotting was conducted to detect the expression of SNC19 using our produced and selected anti-SNC19 monoclonal antibody ZMG9.The dominant form of 120 KD was observed in extracts derived from BCAP37, COLO205 and SW480 cells however no relevant band was observed in SW620 cells. In normal intestinal mucosa and intestinal carcinoma tissues three bands at 120KD, 95 KD and 75KD were observed. Immunohistochemistry exp...
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