No association between SOD2 or NQO1 genotypes and risk of bladder cancer.

SOD2 encodes manganese superoxide dismutase, a mitochondrial enzyme that protects the cell against damage from superoxide free radicals. A common polymorphism, a T ! C transition (Val16Ala), was shown to alter the manganese superoxide dismutase mitochondrial targeting sequence (1). Animal studies have linked reduction in manganese superoxide dismutase activity to increased DNA damage and higher incidence of cancer (2). NQO1 encodes NAD(P)H dehydrogenase (quinone), a flavoprotein that also protects the cell against cytotoxicity, by promoting the two-electron reduction of quinoid compounds to hydroquinones (3). A common polymorphism, a C ! T transition (Pro187Ser), produces significant reductions in enzyme activity in human colon cancer cells (3). Therefore, in the case-control study reported here, we examined the associations between polymorphisms in SOD2 and NQO1 , cigarette smoking, and bladder cancer risk.