Chemically induced mammary gland cancer in the National Toxicology Program's carcinogenesis bioassay.

Incidences of breast cancer change in populations as people migrate from one area of the world to another, suggesting that environmental factors contribute to this disease. There is a continuing effort to identify these environmental factors and the role that exposures to specific chemicals play in this disease. Results from experimental studies show that chemicals identified to cause mammary gland cancer in rodents are frequently mutagenic chemicals, suggesting that genetic damage is an important mechanism for the induction of this cancer. Prevalent classes of chemicals that were identified to cause mammary gland cancer in rodents in studies by the National Toxicology Program include halogenated hydrocarbons, aromatic amino/nitro compounds and epoxide-forming chemicals. Results from these experimental studies will help to elucidate mechanisms and possible causes of breast cancer in humans.