CLONING OF GROWTH FACTORS AND TYROSINE KINASES INVOLVED IN H.pylori-INDUCED GASTRIC CARCINOGENESIS

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Accumulating data suggest involvement of H.pylori infection in the development of gastric cancer. In this study, in order to elucidate roles of H.pylori infection in gastric carcinogenesis, we tried to clone growth factors and tyrosine kinases involved in the development of gastric cancer and adenomas occurred in thymectomised balb/c mice with H.pylori infection, and the following results were obtained ;(1) Balb/c mice were thymectomised 3 days after birth, and infected with H.pylori at 6-8 weeks. Approximately 50% of the mice developed gastric adenoma in the fundic gland.(2) At 9 months after infection RNAs were extracted from adenoma and non-adenoma portions of the fundic glands. After construction of single strand cDNAs, subtraction was performed by using mRNAs from non-infected control mice, and cDNA library was made from the remaining cDNAs.(3) Expression plasmid library was constructed by inserting CMV promotor, transfected to COS cells. Culture medium of the COS cells after 48h incubation was administered to GSMO6 cells, and the plasmid DNA was extracted from the COS cells, the supernatant of which had a significant growth promoting effect on GSMO6 cells. By repeating this procedure, cDNA was finally cloned. We obtained HGF, TGF-α, reg, TNF-α, and IL-1β genes.(4) cDNA was extracted from the COS cells, the growth ability of which was enhanced, and the cDNA was transfected to GSMO6 cells. After selection, genomes were extracted from the proliferating cells, and the cDNA was sequenced.(5) From the procedure as mentioned above, genes involved in NF-kB signaling pathway such as NF-kB, traf-6, NIK, and src and cyclin D1 were obtained.(6) From these data, it is suggested that anti-apoptotic action by various inflammatory cytokines with resulting NF-kB activation is involved in gastric carcinogenesis.