Targeting the DNA repair defect in BRCA mutant cells as a therapeutic strategy

Top Cited Papers
Publisher Website
Google Scholar
Abstract
The discovery that BRCA1/2 mutant cells (defective in the homologous recombination pathway of DNA repair) are spectacularly sensitive to inhibition of the enzyme PARP (involved in base excision repair) suggests a new, low toxicity, approach to the treatment of women with breast cancers caused by BRCA mutations. As the PARP inhibitors have no effect on cells with functional homologous recombination, the hope is that the treatment will be specific for breast cancer cells. PARP-inhibiting chemotherapeutics may be able to make use of a ‘synthetic lethal’ effect as an alternative to conventional nonspecific cytotoxic anticancer treatments. BRCA1 and BRCA2 are important for DNA double-strand break repair by homologous recombination1, and mutations in these genes predispose to breast and other cancers2. Poly(ADP-ribose) polymerase (PARP) is an enzyme involved in base excision repair, a key pathway in the repair of DNA single-strand breaks3. We show here that BRCA1 or BRCA2 dysfunction unexpectedly and profoundly sensitizes cells to the inhibition of PARP enzymatic activity, resulting in chromosomal instability, cell cycle arrest and subsequent apoptosis. This seems to be because the inhibition of PARP leads to the persistence of DNA lesions normally repaired by homologous recombination. These results illustrate how different pathways cooperate to repair damage, and suggest that the targeted inhibition of particular DNA repair pathways may allow the design of specific and less toxic therapies for cancer.