KI-RAS MUTATIONS IN HYLNITROSAMINO)-1-(3-PYRIDYL)-1-BUTANONE-INITIATED AND BUTYLATED HYDROXYTOLUENE-PROMOTED LUNG-TUMORS IN A J MICE/

The promotional effects of butylated hydroxytoluene (BHT) on lung tumo rigenesis induced by 4-(methylnitrosamino)-1 -(3-pyridyl)-1-butanone ( NNK) was evaluated in a two-stage model of lung tumorigenesis in the A /J mouse. Mice were treated in two separate experiments with 1.54 mmol /kg (9.1 mg/mouse) NNK, which induced an average of 8.4 and 9.1 tumors /mouse in the experiments. Animals fed a diet that contained 1 g/kg BH T after administration of the carcinogen in these two experiments demo nstrated an increase of the tumor multiplicity by 63% and 43%. Multipl icity of forestomach tumors was not effected by BHT in the diet. No di fferences in lung tumor morphology were seen as a result of the promot ing effect of BHT. Mutations in the Ki-ras oncogene from lung tumors i nduced by NNK (19 tumors) or by NNK plus a diet containing BHT (34 tum ors) were characterized by polymerase chain reaction, single-strand co nformational polymorphism, and direct sequencing. All 19 NNK-induced t umors not promoted with BHT contained activated Ki-ras genes with GC-> AT transitions at the second base of codon 12. Only 11 of 34 NNK-induc ed and BHT-promoted tumors (32%) had this characteristic Ki-ras altera tion. These data suggest that the NNK-initiated mouse lung tumorigenes is pathway, which involves the specific mutation of the Ki-ras oncogen e, is altered to a predominantly non-ras mechanism when these tumors a re promoted by BHT in the diet. (C) 1994 Wiley-Liss, Inc.