The etiology and prevention of breast cancer.

Metabolism of estrogens via the catechol estrogen pathway is characterized by a balanced set of activating and protective enzymes (homeostasis). Disruption of homeostasis, with excessive production of catechol estrogen quinones, can lead to reaction of these quinones with DNA to form depurinating estrogen-DNA adducts. Some of the mutations generated by these events can lead to initiation of breast cancer. A wealth of evidence, from studies of metabolism, mutagenicity, cell transformation and carcinogenicity, demonstrates that estrogens are genotoxic. Women at high risk for breast cancer, or diagnosed with the disease, have relatively high levels of depurinating estrogen-DNA adducts compared to normal-risk women. The dietary supplements N-acetylcysteine and resveratrol can inhibit formation of catechol estrogen quinones and their reaction with DNA to form estrogen-DNA adducts, thereby preventing initiation of breast cancer.