Because berberine treatment increased oxidative stress and downregulated HR, conditions in which cancer cells would be more reliant on PARP for survival and proliferation, we next tested whether a combination of berberine and PARP inhibitor would be more effective in killing ovarian cancer cells by using MTT viability assay, colony formation assay and flow cytometry analysis of apoptotic cells. Here, PARP1 is linked to ovarian carcinoma.