PARP inhibitors can efficiently kill many breast cancer cells that lack functional Brca1 or Brca2 genes. How do these drugs accomplish this?

A) By increasing the ability of p53 in cancer cells to limit cell proliferation
B) By inhibiting proteins that are normally inhibited by the Brca1 or Brca2 gene products
C) By increasing the occurrences of homologous recombination
D) By inhibiting a DNA repair pathway
E) By increasing the ability of the cancer cells to repair the mutations in their cancer-critical genes