IMPACT OF INHERITED POLYMORPHISMS IN GLUTATHIONE-S-TRANSFERASE M1, MICROSOMAL EPOXIDE HYDROLASE, CYTOCHROME-P450 ENZYMES ON DNA, AND BLOOD PROTEIN ADDUCTS OF BENZO(A)PYRENE-DIOLEPOXIDE

The benzo(a)pyrene (BaP) metabolite benzo(a)pyrene-diolepoxide (BPDE) is strongly implicated as a causative agent of lung cancer. To assess the risk of exposure to BaP, we made a combined analysis of levels of BPDE adducts to hemoglobin (Hb), serum albumin (SA), and lymphocyte DN A in 44 patients with incident lung cancer, as a prototype of a popula tion mainly exposed to tobacco-derived BaP, We also investigated wheth er genetic polymorphisms of cytochrome P450IA1 (CYPIA1), microsomal ep oxide hydrolase (mEH), and glutathione S-transferase M1 (GSTM1), which are involved in BaP metabolism, can be determinants of adduct formati on. BPDE-Hb, BPDE-SA, and BPDE-DNA adducts were quantified as BaP tetr ols released from hydrolysis of macromolecules and measured by high-re solution gas chromatography-negative ion chemical ionization-mass spec trometry to achieve high specificity and sensitivity. Individuals with detectable Hb adducts were positive for SA adducts but not vice versa , suggesting that BPDE-Hb adducts are less informative indicators of B aP exposure. Using PCR methods on DNA, we characterized GSTM1 deletion , CYPIA1 MspI and exon 7 valine variants, and mEH polymorphisms at ami no acid positions 113 (EH3) and 139 (EH4). Levels of BPDE adducts were no different among CYPIA1, mEH, and GSTM1 genotypes, However, individ uals with measurable BPDE-SA adducts were CYPIA1 variant carriers more frequently (P = 0.03). There was a slightly higher percentage of DNA detectable adducts in subjects with CYPIA1 exon 7 valine polymorphism. When subjects were classified by both polymorphisms on the mEH gene, those with two slow alleles (EH3 homozygous mutated) and no fast allel es (EH4 homozygous wild type) had a lower frequency of BPDE-SA adducts and no DNA adducts (P = 0.06). These results are based on a small num ber of observations thus far, but this exploratory study suggests that CYPIA1 and mEH variants might have an impact on BPDE exposure markers such as BPDE-SA adducts. Chemical specificity in adduct measurements is important to identify the biomarkers that reflect BaP exposure more accurately.