MP92-15 SUPPRESSION OF CHAPERONE-MEDIATED AUTOPHAGY: A NOVEL MECHANISM OF ACTION OF SILIBININ AGAINST BLADDER AND RENAL CANCER

Abstract

You have accessJournal of UrologyKidney Cancer: Basic Research & Pathophysiology III1 Apr 2016MP92-15 SUPPRESSION OF CHAPERONE-MEDIATED AUTOPHAGY: A NOVEL MECHANISM OF ACTION OF SILIBININ AGAINST BLADDER AND RENAL CANCER Jin Zeng, Wei Liu, Feng Li, Yi Sun, Lei Li, Xinyang Wang, and Dalin He Jin ZengJin Zeng More articles by this author , Wei LiuWei Liu More articles by this author , Feng LiFeng Li More articles by this author , Yi SunYi Sun More articles by this author , Lei LiLei Li More articles by this author , Xinyang WangXinyang Wang More articles by this author , and Dalin HeDalin He More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2016.02.2648AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Chaperone-mediated autophagy (CMA) contributes to cellular quality control through the selective degradation of cytosolic proteins in lysosomes. Dysregulation of CMA activity occurs in age-related disorders and cancers. Chemical regulation of CMA is not currently possible, owing to the lack of information on the signaling mechanisms. A bulk of evidence from others and us suggests that silibinin, a natural flavonoid from milk thistle, exerts strong pleiotropic anticancer capabilities in various cancers. However, underlying mechanisms are poorly understood. The aim of this study was to investigate the role of CMA in silibinin-induced cell death in bladder cancer (BCa) and renal cell carcinoma (RCC). METHODS Human BCa 5637 and T24 cell lines and RCC ACHN and 769-P cell lines served as the model system in vitro and in vivo. Cell viability was determined by MTS assay. Lysosomes were isolated from cells by iodixanol-based density gradient centrifugation. The expression of two key CMA components heat shock-cognate chaperone of 70 kDa (hsc70) and lysosome-associated membrane protein type 2a (LAMP2a) on lysosomes were examined by western blot after silibinin treatment. Co-immunoprecipitation was used to determine the interaction between hsc70 and LAMP2a. CMA activity was monitored by in vitro lysosome binding and uptake assay. RNase and GAPDH, two well-characterized CMA substrates, were used in this functional assay allow tracking CMA activity. Immunohistochemistry analysis was performed for evaluating hsc70 and LAMP2a expression in BCa and RCC xenografts after oral silibinin in vivo. RESULTS Exposure of BCa and RCC cells to silibinin resulted in significant inhibition of cell growth. Downregulation of hsc70 and LAMP2a on lysosomes were observed after silibinin treatment. Overexpression of exogenous hsc70 or LAMP2a attenuated silibinin-induced cell death, while knocking down hsc70 or LAMP2a sensitized cells to death by silibinin. Furthermore, silibinin inhibited the interaction between hsc70 and LAMP2a on lysosome in both BCa and RCC cells. Additionally, silibinin treatment decreased the ability of substrates to be taken up by the lysosomes and inhibited the lysosomal degradation of substrates, suggesting the suppression of CMA activity. Oral silibinin suppressed the growth of BCa and RCC xenografts in vivo, which were accompanied with downregulation of hsc70 and LAMP2a. CONCLUSIONS This study reveals suppression of CMA as a novel mechanism for silibinin′s anti-proliferative effect, and suggests targeting CMA pathway may have antitumor potential against BCa and RCC. © 2016FiguresReferencesRelatedDetails Volume 195Issue 4SApril 2016Page: e1167 Advertisement Copyright & Permissions© 2016MetricsAuthor Information Jin Zeng More articles by this author Wei Liu More articles by this author Feng Li More articles by this author Yi Sun More articles by this author Lei Li More articles by this author Xinyang Wang More articles by this author Dalin He More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...