CP-8 and CP-23 display synergistic antiproliferative activity in combination with olaparib, niraparib and talazoparib. A. MDA-MB-231 cells (500 cells/well) were treated with nitroalkene analogs (0–6 μM) on days 0, 2, and 6. Growth inhibition was determined by measuring relative ATP levels on day 7 via CellTiter-Glo. B-D. MDA-MB-231 cells (500 cells/well) were treated with PAPR inhibitors olaparib, niraparib, and talazoparib on days 0, 2, and 6. EC50 values were determined as in (A). E-F. Decrease of EC50 values of PARPi co-treated with CP-8 or CP-23 in increasing concentrations. Statistical analysis was done by two-way ANOVA; Average ± SEM n = 3. G-F. Drug combination synergy calculations were performed using the SynergyFinder and HSA methods. MDA-MB-231 cells plated as in A-D were treated with 0–6 μM of nitroalkene and increasing doses of PARP inhibitors (olaparib 0–50 μM, niraparib 0–50 μM, and talazoparib 0–3.1 μM). Average ± SEM n = 3.