Bcl-2 overexpression reduces cisplatin cytotoxicity by decreasing ER-mitochondrial Ca(2+) signaling in SKOV3 cells

Recent studies have revealed that a small amount of cisplatin can penetrate into the nucleus and induce intranuclear DNA damage. Specifically, most cisplatin accumulates in and stresses different organelles, including mitochondria, endoplasmic reticulum (ER) and the cytosol, where apoptosis signaling is activated and magnified. Bcl-2, which is mainly localized to ER and mitochondria, is identified as a key regulator of survival and apoptosis. Bcl-2 is reported to block cisplatin-induced apoptosis via regulating Ca(2+) signaling in a variety of cancer cell lines. However, its target molecule and the mechanism responsible for its inhibitory effect in ovarian cancer are undefined. The present study revealed that Bcl-2 overexpression reduced cisplatin-induced growth inhibition and apoptosis in SKOV3 human ovarian cancer cells. Furthermore, Bcl-2 inhibited cisplatin-induced Ca(2+) release from the ER to the cytoplasm and mitochondria, which reduced cisplatin-induced ER stress-mediated apoptosis through the mitochondrial apoptotic pathway. The overexpression of Bcl-2 inhibited the cisplatin-induced increase in the number of ER-mitochondrial contact sites in SKOV3 human ovarian cancer cells. In addition, the present study provided evidence that Bcl-2 reduced the anticancer activity of cisplatin towards ovarian cancer cells in vivo. These results revealed that Bcl-2 attenuates cisplatin cytotoxicity via downregulating ER-mitochondrial Ca(2+) signaling transduction. Thus, Bcl-2 which may be a potential therapeutic target for ovarian cancer.