PARP1 and cancer: PARP inhibitors exert cytotoxic effects through the inhibition of the catalytic activity of PARP1/PARP2 by trapping PARP–DNA complexes, thereby preventing DNA replication and transcription.8 Potent and specific inhibitors of PARP have been shown to sensitise cancer cells to the DNA-damaging effects of cytotoxic chemotherapy and radiotherapy.9 One of the key features of the DNA repair pathway is redundancy or the capacity for alternative proteins or molecular pathways to compensate for specific repair deficiencies.