MP36-11 AUTOPHAGY IS ACTIVATED IN HUMAN BLADDER CANCER AND REQUIRED FOR CANCER CELL GROWTH

Abstract

INTRODUCTION AND OBJECTIVES: Macroautophagy, also known as type II programmed cell death, is a regulated catabolic pathway to degrade cellular organelles and macromolecules. The role of autophagy in cancer is complex and may differ depending on tumor type or context. Here, we investigated the activated basal autophagy in bladder cancer cells and its roles in maintaining cancer cell growth. METHODS: Human immortalized uroepithelium (SV-Huc-1) and bladder cancer cells including RT-4 (grade I), 5637 (grade II), HT1376 and T24 (grade III) were used. We also included human prostate cancer cells (Rv1 and PC3), breast cancer cell (MCF-7) and embryonic kidney cancer cell (293T) as reference cells. The cell viability was accessed by WST-8. Autophagy was detected by the expression level of LC3-II protein. Human bladder tumor tissue array (TMA; 12 cases, paired with normal tissue) was used to detect the LC3 expression level. Detection of apoptosis level was measured by caspase 3/7 activation, caspase 3 cleavage and TUNEL assays. The ROS generation, mitochondria membrane potential in cells treated with autophagy inhibitors was assayed by staining with H2DCFCA and JC-1 dyes, respectively, and subsequently subjected to flow cytometry analysis. Disruption of lysomome membrane (LMP) by was detected by immunofluorescent of cathepsin-D in cells treated with CQ. RESULTS: We found bladder cancer cells exhibited high basal level of autophagy compared to prostate, breast or embryonic kidney cancer cells. Immunohistochemistry (IHC) detection of LC3 in human bladder TMA showed increased level of LC3 in bladder tumor tissues compared to their paired normal tissues. In the cell-based experiment, we found that autophagy inhibitors alone inhibited bladder cancer cell growth and increased apoptosis. The ROS generation and MMP disruption were not detected in cells treated with CQ or HCQ. Immunofluorescent detection of cathepsin-D in cells treated with CQ showed dispread pattern in the cytosol, suggesting the disruption of LMP in CQ-treated bladder cancer cells. CONCLUSIONS: Our results showed that human bladder cancer exhibits high basal level of autophagy. Autophagy inhibitors showed significant effects on the growth of bladder cancer cells by disruption of lysosome function and elevation of apoptotic cell death.