Bcl-2 Overexpression Inhibits Generation of IntracellularReactive Oxygen Species and Blocks Adriamycin-inducedApoptosis in Bladder Cancer Cells

Abstract

Resistance to induction of apoptosis is a major obstacle for bladder cancer treatment. Bcl-2 is thought to beinvolved in anti-apoptotic signaling. In this study, we investigated the effect of Bcl-2 overexpression on apoptoticresistance and intracellular reactive oxygen species (ROS) generation in bladder cancer cells. A stable Bcl-2overexpression cell line, BIU87-Bcl-2, was constructed from human bladder cancer cell line BIU87 by transfectingrecombinant Bcl-2 [pcDNA3.1(+)-Bcl-2]. The sensitivity of transfected cells to adriamycin (ADR) was assessed byMTT assay. Apoptosis was examined by flow cytometry and acridine orange fluorescence staining. IntracellularROS was determined using flow cytometry, and the activities of superoxide dismutase (SOD) and catalase (CAT)were also investigated by the xanthinoxidase and visible radiation methods using SOD and CAT detection kits.The susceptibility of BIU87-Bcl-2 cells to ADR treatment was significantly decreased as compared with controlBIU87 cells. Enhanced expression of Bcl-2 inhibited intracellular ROS generation following ADR treatment.Moreover, the suppression of SOD and CAT activity induced by ADR treatment was blocked in the BIU87-Bcl-2case but not in their parental cells. The overexpression of Bcl-2 renders human bladder cancer cells resistant toADR-induced apoptosis and ROS might act as an important secondary messenger in this process.