Resistance to chemotherapy-induced apoptosis via decreased caspase-3 activity and overexpression of antiapoptotic proteins in ovarian cancer

Goals. Resistance to cisplatin is the main reason for treatment failure in ovarian cancer. Apoptosis is the main mechanism of action of most cancer chemotherapeutic agents. The apoptosis-associated proteins expressed in cisplatin-sensitive (A2780, COC1) and -resistant (A2780/DDP, COC1/DDP) ovarian cancer cell lines, as well as their effects on caspase-3 activity in these cells, were studied by reverse transcriptase polymerase chain reaction and Western blot analysis. Methods. The apoptotic ratios of A2780, COC1, A2780/DDP, and COC1/DDP cells after treatment with cisplatin were measured by flow cytometry. Results. Expression of Bcl-2 and Bcl-X-L in A2780/DDP and COC1/DDP cells was significantly higher than that in A2780 and COC1 cells, respectively. Expression of Bax and Bcl-Xs did not differ in cisplatin-resistant and -sensitive cells. Caspase-3 activity was reduced markedly and apoptotic ratios were significantly lower in A2780/DDP and COC1/DDP cells than in A2780 and COC1 cells after treatment with cisplatin. Conclusion. We conclude that overexpression of antiapoptotic proteins Bcl-2 and Bcl-X-L and down-regulation of caspase-3 activity may be associated with cisplatin resistance in human ovarian cancer.