Since PARP1 inhibition induces accumulation of DNA damage in BRCA1-deficient cells, we tested if inhibition of EZH2 enhances the effect of the PARP inhibitor olaparib in BRCA1-mutated and BRCA1-reconstituted MDA-MB-436 human breast carcinoma cells [37, 38]. This evidence concerns the gene PARP1 and breast carcinoma.