Using biomarkers of genetic susceptibility to enhance the study of cancer etiology.

There has been increasing interest in the interaction of genetic susceptibility and xenobiotic exposures in cancer etiology. Study of gene-environment interactions may increase our ability to characterize relatively low population risks if a substantial proportion of the population cancer burden is attributed to high risk among a smaller group of genetically susceptible members. Further, these studies may provide insight into the mechanism of carcinogenesis, which can help establish the biologic plausibility of an exposure-cancer relationship. Biologic processes important in tumorigenesis that exhibit substantial interindividual differences may function as susceptibility factors. Potential examples include polymorphic enzymes, which activate and detoxify procarcinogens and carcinogens (e.g., certain P450 enzymes, N-acetyltransferase [NAT2], glutathione S-transferase M1), and variation in the capacity to repair DNA. Biologic assays are now available to evaluate many of these functions at the DNA and phenotype level and can be readily incorporated into studies of cancer etiology.