Enhanced lung tumor development in tobacco smoke-exposed p53 transgenic and Kras2 heterozygous deficient mice

A/J mice bearing either a mutation in the p53 gene or a Kras2 heterozygous deficiency were investigated for their susceptibility to tobacco smoke-induced lung tumorigenesis. Transgenic mice and their wild-type littermates were exposed to mainstream tobacco smoke (MS) for 5 mo, followed by 4 mo of recovery in filtered air. In sham (filtered air) groups, p53 transgenic mice did not exhibit a higher tumor multiplicity but did exhibit larger tumors, with tumor load increased 3.6-fold, when compared with wild-type mice. With exposure to MS, tumor multiplicity was increased 60% but there was a strikingly increased tumor load (15.9-fold) in p53 transgenic mice. Increased tumor load (5.3-fold) but not tumor multiplicity was seen in MS-exposed Kras2 heterozygous deficient mice. Interestingly, MS exposure did not increase benzo[a]pyrene-induced lung tumorigenesis when MS exposure was initiated after BaP treatment. These results indicate that a p53 mutation or loss of a Kras2 allele increases susceptibility to MS-induced lung tumor development.