PARP1 and breast cancer: Synergistic activity is seen when the PARP inhibitor talazoparib is used in combination with the DNA damaging agent temozolomide in BRCA1 mutant cells.24 It has been shown that wtp53 expression decreases sensitivity of breast cancer cells to PARP inhibition25 and ciprofloxacin blocks the MCM2–7 complex.26 We asked if increased cytotoxity of PARP inhibition could be detected in the presence of mtp53 if DNA was damaged by alkylation.