BRCA1 CpG Island Hypermethylation Predicts Sensitivity to Poly(Adenosine Diphosphate)- Ribose Polymerase Inhibitors

Recently, Fong et al reported the antitumor activity of the poly(adenosine diphosphate)-ribose polymerase (PARP) inhibitor olaparib (AZD2281; KU-0059436) in patients with BRCA1/BRCA2 germline mutated ovarian cancer. Female BRCA1 and BRCA2 mutation carriers have a significantly elevated lifetime risk of breast and ovarian cancer. BRCA1 and BRCA2 proteins play major roles in DNA double-strand break repair through homologous recombination, and inhibition of DNA single-strand break repair leads to the accumulation of double-strand breaks. These potentially lethal events in homologous recombination-deficient cells could be exploited for therapeutic purposes. The PARP-1 protein is essential for single-strand break repair, and inhibition of PARP leads to persistence of DNA lesions normally repaired by homologous recombination.