SEQUENCING ANALYSIS OF HA-RAS, KI-RAS, AND N-RAS GENES IN RAT URINARY-BLADDER TUMORS INDUCED BY N-[4-(5-NITRO-2-FURYL)-2-THIAZOLYL]FORMAMIDE (FANFT) AND SODIUM SACCHARIN

Male F344 rats were fed N[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (F ANFT) for up to 4 wk, then given the basal diet with or without 5% sod ium saccharin for up to 100 wk. In a previous study, we demonstrated p oint mutations in codons 12 and 61 of Ha-ras gene among eleven transit ional cell carcinomas (TCC), one undifferentiated carcinoma, and two s arcomas of the urinary bladder (Mol Carcinogen 3:210-215, 1990). In th is study, Ha-ras, Ki-ras, and N-ras sequences were examined by polymer ase chain reaction (PCR) and direct DNA sequencing. The results confir m the point mutation in codon 61 (CAA to CGA in 5 TCCs and to CTA in o ne TCC) of the Ha-ras gene. Mutation at codon 12 was not confirmed. No mutation was found in the Ki-ras gene. Sequences of the N-ras gene ex ons 1 and 2 were determined, and no mutations was detected. These resu lts suggest the involvement of activated Ha-ras gene, but not Ki-N or N-ras gene, in rat urinary bladder carcinogenesis induced by FANFT. Su bsequent sodium saccharin administration did not affect the changes in Ha-ras gene. (C) 1993 Wiley-Liss. Inc.