BRCA in breast cancer: from risk assessment to therapeutic prediction.

BRCA1/2 mutations are the most commonly identified germ line gene mutations in patients with hereditary breast cancer. These proteins have many critical cellular functions, including repair of DNA double-strand breaks. The role of defective BRCA1/2 as a predictor of response to DNA-damaging agents has been studied extensively in preclinical models, but prospective clinical validation is lacking. Poly [ADP-ribose] polymerase (PARP) inhibitors illustrate the concept of synthetic lethality in cells with defective BRCA1/2 and numerous PARP inhibitors are being evaluated in patients with BRCA1/2-associated tumors. BRCA1/2 mutation or functional loss will likely serve as a useful predictive biomarker of response to treatment with PARP inhibitors.