PARP1 and ovarian cancer: By sensing DNA-strand breaks and orchestrating base excision repair, PARP1 has an important role in the repair of oxidative DNA damage.15, 16, 17 PARP1 also becomes hyperactivated in cells with defective HRR,18, 19 and HRR-defective cells are particularly sensitive to PARP inhibition.18, 19, 20 Because berberine can induce oxidative stress and downregulate HRR, conditions in which cells are more reliant on PARP1 for survival, we speculated that berberine-treated ovarian cancer cells might be more sensitive to PARP inhibition.