Fig. 4.

Mechanism for synthetic lethality in breast cancer susceptibility gene (BRCA) 1/2 deficient cancer. Poly ADR-ribose polymerase (PARP) inhibition produces tumor-selective synthetic lethaity. When PARP action is inhibited, SS are converted to double strand break (DSB) at replication. In cells with functional HR pathway, the DSB will be repaired. In cells with a dysfunctional HR pathway, as is the case with BRCA 1 and 2, the lesions go unrepaired and cell death ensues. HR, homologous recombination; SSB, single-strand break. Reprinted from Saijo [70].