Genetic polymorphism and cancer risk.

Inter-individual variability in carcinogen metabolism has been attributed in part to the polymorphic expression of several phase I and II detoxification enzymes. The role of these genetic polymorphisms in cancer susceptibility has been most extensively evaluated for isozymes of cytochrome P450 (CYP1A1, CYP2D6, and CYP2E1), N-acetyltransferase (NAT1 and NAT2), glutathione S-transferase (GSTM1, GSTT1, and GSTP1), microsomal epoxide hydrolase, and NAD(P)H:quinone oxidoreductase. Our understanding of the genetic basis of cancer risk has been enhanced most recently by establishment of genotype-phenotype correlations in humans and identification of numerous diverse factors, both genetic and environmental, that can modify risk.