HeLa (A) and Caski (B) cells were treated with the PARP inhibitor BYK (10 μM), the chemotherapeutic drug cisplatin (CDDP; 2 μM), or both in combination as indicated. Cells were collected and stained with crystal violet at day 0, 2, 4, 6 and 8 (top panel). Cell survival was quantified for each of the time points by measuring absorbance at O.D. 595nm (bottom panel). Each point represents the mean ± SEM (n = 4; Fisher’s LSD test; * p < 0.05).