Induction of c-fos and c-myc oncogene expression in the pyloric mucosa of rat stomach by N-methyl-N'-nitro-N-nitrosoguanidine and taurocholate.

The induction of c-fos and c-myc expression in the pyloric mucosa of 8-week-old F344 male rats after oral administration of the glandular stomach carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), or the tumor-promoter, taurocholate, was examined by Northern blotting. MNNG at doses of 5-50 mg/kg body weight dose-dependently induced transient increase of up to 30-fold c-fos expression with a maximum after 30 min, and of 8-fold c-myc expression with a maximum after 3 h. It also induced up to 3-fold increase in S-phase cells in the proliferation zone of the pyloric mucosa after 16 h. Similar effects were observed with sodium taurocholate at doses of 200-800 mg/kg body weight. These results suggest that c-fos and c-myc oncogenes play a role in stomach carcinogenesis.