Associations of oxidative balance-related exposures with incident, sporadic colorectal adenoma according to antioxidant enzyme genotypes

Purpose: Previous research found inverse associations between oxidative balance and risk of colorectal adenoma. However, these measures were limited to extrinsic (dietary and lifestyle) exposures and did not account for intrinsic factors, specifically antioxidant enzymes responsible for cellular defense against oxidative stress. We investigated whether the association between an oxidative balance score (OBS) and colorectal adenoma may vary according to polymorphisms in genes that encode three antioxidant enzymes: Manganese superoxide dismutase (SOD2), catalase (CAT), and glutathione-S-transferase P1 (GSTP1). Methods: Using data pooled from three colonoscopy-based case-control studies of incident, sporadic colorectal adenoma, we constructed an OBS reflecting pro- and antioxidant exposures. We used multivariable logistic regression to assess whether the association between the OBS and colorectal adenoma differed according to polymorphisms in the genes encoding the antioxidant enzymes. Results: OBS was inversely associated with colorectal adenoma; adenoma risk was not associated with the genetic polymorphisms, and there was no consistent pattern of effect modification by individual genotypes or combined gene scores. Conclusions: Variations in the antioxidant enzyme genes SOD2, CAT, and GSTP1 do not seem to substantially modify associations of environmental exposures related to oxidative balance with risk for sporadic colorectal adenoma.