p53 haploinsufficiency profoundly accelerates the onset of tongue tumors in mice lacking the xeroderma pigmentosum group A gene.

Mice lacking the xeroderma pigmentosum group A gene (XPA-/- mice), which have a complete deficiency in nucleotide excision repair (NER), are highly predisposed to tongue squamous cell carcinoma (SCC) when exposed to 4-nitroquinoline 1-oxide (4NQO). To explore the effects of the interaction of the NER machinery with p53 in oral tumorigenesis, we generated an XPA-/- mouse strain carrying mutant alleles for p53. This mouse model of 4NQO carcinogenesis demonstrated that despite the same tumor frequency, XPA-/-p53+/- mice reached 100% SCC incidence at 25 weeks compared with 50 weeks for XPA-/-p53+/+ littermates. XPA-/-p53-/- mice succumbed to spontaneous thymic lymphomas before the development of tongue tumors (before 13 weeks of age). SCC originated in XPA-/-p53+/- mice maintained the p53+/- genotype and the retained wild-type p53 allele appeared to be structurally intact. Only one of 20 XPA-/-p53+/+ SCC showed a missense mutation of p53. Collectively, the accelerated tongue tumor growth may be a consequence of haploinsufficiency but not of mutation of p53 in the context of NER deficiency.