A panel of hybrids of HeLa and a normal human fibroblast differing in tumorigenicity in nude mice was screened for RNA levels specific for 21 oncogenes and for human papillomavirus 18 and for papillomavirus were detected. The levels of three of these oncogenes. Transcripts for 15 of these oncogenes were found to correlate with tumorigenicity. These were fos and ets transcripts, which were present at a higher level in tumorigenic hybrids than in non-tumorigenic hybrids and myb transcripts, which were higher in the non-tumorigenic hybrids. Fos protein levels correlated with fos transcript levels. A non-tumorigenic hybrid, when infected with murine sarcoma virus, did not show alteration in the levels of fos, ets or myb transcripts. A panel of human SV80 cells transfected for the proviral mos gene has been generated. These transfectants differ in tumorigenic potential in nude mice. Explants of the tumorigenic members of this panel do not show any alteration in the size or amount of immunoprecipitable SV40 T antigen consistent with an immunological selection against T antigen expression during tumor formation. RNA has been prepared from the members of the panel for an examination of the levels of mos-specific transcripts. An activated N-ras gene cloned previously from human gastric adenocarcinoma material has been characterized using DNA sequencing and transfection assays of in vitro ligated DNA fragments.
