The interaction between alcohol consumption and GSTM1 genotype on polycyclic aromatic hydrocarbon-DNA adduct levels in breast tissue

We investigated the association between alcohol consumption, GSTM1 genotype, and polycyclic aromatic hydrocarbon (PAH)-DNA adduct levels in breast tissue. Women referred for breast surgery were enrolled prior to surgery, responded to an interview, and gave a blood sample. Women diagnosed with ductal carcinoma in situ and invasive ductal or lobular cancer were defined as cases, and women with benign conditions without atypia were defined as controls. Paraffin-embedded tumor and nontumor tissue from cases and benign tissue from controls were retrieved from the pathology samples. GSTM1 genotype status was determined by PCR using WBC DNA, and PAH-DNA adduct levels were measured in breast tissue using immunohistochemistry. In tumor and nontumor tissue from cases, the GSTM1-null genotype was associated with increased adduct levels among current alcohol consumers but not among nondrinkers. In nontumor tissue, the interaction between genotype and alcohol consumption was significant (P=0.02), but in tumor tissue, the interaction did not achieve statistical significance (P=0.10). In benign tissue from controls, there was no association between genotype and adducts, regardless of drinking status. Among subjects with the null genotype who drank alcohol, adduct levels were significantly higher in tumor and nontumor tissue from cases than in benign tissue from controls. These results indicate the presence of a novel gene-lifestyle interaction that influences PAH-DNA adduct levels in breast tissue from cases but not controls. This apparent difference in PAH metabolism in response to alcohol may be an important clue as to how alcohol influences breast cancer risk.