The molecular genetics of breast cancer and targeted therapy.

Breast cancer is a complex, molecular disease, in which a number of cellular pathways involving cell growth and proliferation, such as the MAPK, RB/E2F, P13K/AKT/mTOR, and TP53 pathways, are altered. These pathways represent molecular mechanisms that are composed and regulated by various genes. The genes that are altered in terms of cell growth and proliferation include the oncogenes HER2, c-MYC, and RAS, the ER genes, and the genes for cell cyclin D1 and E, and the tumor suppressor genes RB, TP53, and PTEN, and the breast cancer susceptibility genes BRCA1 and BRCA2. Although the nature of breast cancer is complex and has frustrated previous attempts at treatment or prevention, the elucidation of its molecular nature over the last several decades is now providing targets for effective therapies to treat the disease and hopefully one day to prevent it.