[Novel transforming genes detected in human stomach cancer cells]

The DNAs of six human stomach cancer cell lines were analysed, and specific gene amplification was observed; namely, an 8-fold amplified c-Ki-ras-2 gene (1 case) and a 20-fold amplified c-myc gene (1 case). In addition, it was found that a single 11-kbp-Eco-R1 fragment, having weak homology to the Ki-ras gene, was amplified 5-10 fold in three out of the six cell lines. The DNAs of two of these three cell lines gave rise to foci upon transfection into NIH3T3 cells and the primary and secondary transformants seemed to carry a similar 11-kbp-Eco-R1 fragment. It was also found that one of the DNAs from human stomach cancers gave rise to NIH3T3 cell foci upon DNA transfection. DNAs of secondary transformants commonly retained six Eco-R1 fragments that contained human Alu repeats. The size of this gene was estimated to be about 50 kbp. The Southern blot hybridization profile of this gene revealed it to be clearly different from known active human oncogenes. Furthermore, about 70% of this gene has been isolated and portions of it used as probes to test for homologies to known viral oncogenes. The gene appears to be unrelated to 14 viral oncogenes so far tested.