PARP1 and cancer: Preclinical data, including that generated with a limited array of tumour cell line xenografts, suggest that PARP inhibitors can act as single agents to selectively kill cancers with BRCA1 or BRCA2 mutations, and phase I clinical trial results confirm that PARP inhibitors have some single-agent activity in cancers with BRCA1/2 mutations (Fong et al, 2009).