K-RAS MUTATIONS IN LUNG-TUMORS FROM A J AND A/JXTSG-P53 F1-MICE TREATED WITH 4-(METHYLNITROSAMINO)-1-(3-PYRIDYL)-1-BUTANONE AND PHENETHYL ISOTHIOCYANATE/

The purpose of this study was to evaluate the effects of the loss of a p53 allele and phenethyl isothiocyanate (PEITC) pre-treatment on the tumorigenicity of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and K-ras mutation frequency in a hybrid mouse model. Male TSG-p53 'k nock-out' mice were bred with A/J female mice to produce (A/J X TSG-p5 3) F-1 mice either homozygous (p53 +/+) or heterozygous (p53 +/-) for p53 alleles. These mice, together with female A/J mice, were treated a t 6-8 weeks of age with NNK or dosed with PEITC prior to administratio n of NNK. The A/J mice treated with NNK had a 100% incidence of lung t umors, with 9.7 +/- 3.4 tumors/mouse. A/J mice pre-treated with PEITC prior to NNK administration had 3.5 +/- 2.1 lung tumors/animal, althou gh the incidence remained at 100%. In (A/J X TSG-p53) F-1 mice with ei ther the p53(+/-) or p53(+/+) genotype PEITC pre-treatment significant ly decreased tumor incidence (100 to 40 and 36%, respectively) and mul tiplicity (2.0 +/- 0.5 to 0.5 +/- 0.4 and 2.1 +/- 0.5 to 0.5 +/- 0.4, respectively), indicating that PEITC is an effective chemopreventive a gent in both A/J mice and (A/J X TSG-p53) F-1 mice. Analysis of lung t umor DNA from A/J mice treated with NNK or NNK/PEITC indicated that 15 of 17 (88%) and 20 of 23 (87%) of the tumors, respectively, contained G-->A transitions at the second base of codon 12 in the K-ras gene. S imilarly, in lung tumors from (A/J X TSG-p53) F-1 mice treated with NN K or NNK/PEITC 29 of 30 (96%) and 9 of 10 (90%), respectively containe d G-->A transitions at the second base of codon 12 of the K-ras gene. No mutations of the p53 gene were found in any of the tumors analyzed, suggesting minimal involvement of this gene in the development of lun g adenomas. These data indicate that absence of a p53 allele in (A/J x TSG-p53) F-1 mice does not alter the incidence or multiplicity of NNK -induced lung tumors and that PEITC inhibition of NNK tumorigenesis do es not affect the frequency or spectrum of K-ras gene mutations found consistently with NNK carcinogenesis.