Effect of DNA repair gene polymorphisms on BPDE-DNA adducts in human lymphocytes

To determine whether variations in DNA repair genes are related to host DNA damage, we investigated the association between polymorphism in the XPD gene (codon 199, 312, 751) and the XRCC1 gene (codon 194, 399) and the presence of benzo(a)pyrene diolepoxide adducts to lymphocyte DNA (BPDE-DNA) in a group of male patients with incident lung cancer, all current smokers. BPDE-DNA adducts were analyzed by high-resolution gas chromatography-negative ion chemical ionization-mass spectrometry. XPD and XRCC1 genotypes were identified by PCR-RFLP. XRCC1 and XPD genotypes did not affect the levels and proportion of detectable BPDE-DNA adducts. The patients were also genotyped for the GSTM1 polymorphism, given its role in the detoxification of BPDE. Individuals with the GSTM1 deletion had significantly higher levels of BPDE-DNA adducts when they were XPD-Asp312Asp+Lys751Lys than carriers of at least one variant allele. No such association was found with the XRCC1 genotypes. Because of the small study population (n = 60), further statistical analysis of possible gene-gene and gene-environment would not be informative. This is the first study analysing the specific BPDE-DNA adduct in vivo with regard to polymorphic repair genes (XPD, XRCC1) and xenobiotic metabolizing gene (GSTM1). Our results raise the possibility that the XPD-Asp312Asp+Lys751Lys genotype may increase BPDE-DNA damage; this effect might be evident in individuals who are especially likely to have accumulated damage, probably because of lower detoxification capacity and high environmental exposure.