PARP1 and cancer: Being frequently mutated or overexpressed in human cancers, the ubiquitin and UBL pathways offer a spectrum of attractive drug targets, and with the recent approval of PARP inhibitor olaparib/LynparzaTM (AstraZeneca) by the European Medicines Agency and the US Food and Drug Administration for the treatment of BRCA-mutated, high-grade serous epithelial ovarian cancer, the precedent is now set for DDR inhibitors in the clinic.