Polymorphisms in XPD and TP53 and mutation in human lung cancer

The pattern of somatic mutations in TP53 is distinct for particular cancers and carcinogenic exposures, providing clues to disease etiology, e.g. G:C-->T:A mutations in TP53 are more frequently observed in smoking-associated lung cancers. In order to investigate possible causes and mechanisms of lung cancer susceptibility differences, the TP53 gene was sequenced in a case-only study of lung cancers (206 men and 103 women). Our primary hypothesis was that the TP53 mutation spectrum is influenced by polymorphisms in genes involved in DNA repair and apoptosis. We observed a TP53 mutation frequency in exons 5-8 of 25%. Functional polymorphisms in XPD (Asp312Asn, rs1799793 and Lys751Gln, rs1052559), a protein required for nucleotide excision repair and with roles in p53-mediated apoptosis, were modestly associated with G:C-->T:A mutations in TP53 in lung tumors [Asp/Asn312 + Asn/Asn312 and/or Lys/Gln751 + Gln/Gln751 versus Asp/Asp312 + Lys/Lys751; odds ratio (OR) 2.73, 95% confidence interval (CI) 0.98-7.61], consistent with the role of this protein in repair of bulky carcinogen-DNA adducts. In addition, a TP53 polymorphism (Arg72Pro, rs1042522) with a known role in the efficiency of apoptosis was also associated with the presence of a TP53 mutation (Pro/Arg72 or Pro/Pro72 versus Arg/Arg72; OR 2.25, 95% CI 1.21-4.17) or a G:C-->T:A mutation in TP53 (Pro/Arg72 or Pro/Pro72 versus Arg/Arg72; OR 2.42, 95% CI 0.97-6.04). An interaction between the XPD variant alleles (Asn312 and Gln751) and the TP53 Pro72 allele was observed for TP53 mutations (any TP53 mutation P(int) = 0.027, G:C-->T:A TP53 mutation P(int) = 0.041). The statistical interaction observed in our study is consistent with the observed biological interaction for XPD and p53 in nucleotide excision repair and apoptosis. In conclusion, differences in TP53 mutation spectra in lung tumors are associated with several genetic factors and may reflect differences in lung cancer susceptibility and carcinogenesis.