Cisplatin-induced cytotoxicity and apoptosis, and expression of p21 in C13* and OV2008 cells. (A) Dose-response curves for C13* and OV2008 cells following treatment with cisplatin. (B) Cisplatin-induced apoptosis at different time points (20 μM). (C) Comparison of p21 protein levels between paired cell lines. (D) The p21 expression ratio of C13* to OV2008 cells. (*, p < 0.05).