MP48-08 HEAT SHOCK PROTEIN 70 MEDIATED SILIBININ-ACTIVATED MITOCHONDRIAL APOPTOTIC SIGNALING PATHWAY IN BLADDER CANCER

Abstract

You have accessJournal of UrologyBladder Cancer: Basic Research & Pathophysiology II1 Apr 2017MP48-08 HEAT SHOCK PROTEIN 70 MEDIATED SILIBININ-ACTIVATED MITOCHONDRIAL APOPTOTIC SIGNALING PATHWAY IN BLADDER CANCER Jin Zeng, Yule Chen, Kaijie Wu, Yi Sun, Lei Li, and Dalin He Jin ZengJin Zeng More articles by this author , Yule ChenYule Chen More articles by this author , Kaijie WuKaijie Wu More articles by this author , Yi SunYi Sun More articles by this author , Lei LiLei Li More articles by this author , and Dalin HeDalin He More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.1489AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES We previously identified intravesical silibinin, a natural flavonoid, as a novel and effective chemopreventivetherapy against bladder cancer (BCa), which were accompanied with its proapoptotic effects. However, the exact mechanisms are not thoroughly understood. Heat shock proteins (Hsps) have been identified as key determinants of cancer cell survival, which can modulate apoptosis by directly interacting with components of the apoptotic machinery. Manipulation of Hsps by chemical agents represents a viable strategy against cancer. Therefore, the purpose of this study was to examine the role of Hsps in regulating silibinin-induced apoptosis in BCa. METHODS Human BCa cell line RT4 and T24 served as the model system in vitro and in vivo. The expression of Hsps, heat shock factor-1(HSF1) and apoptosis related molecules after silibinin treatment were examined by western blot. Co-immunoprecipitation was used to determine the interaction between apoptotic protease activating factor-1 (Apaf-1) and Hsp70 or pro-caspase 9. Both nude mice xenografts and orthotopic rat bladder cancer tissues were analyzed for apoptosis molecular alterations after oral or intravesical silibinin treatment in vivo. RESULTS Exposure of BCa cells to silibinin resulted in significant downregulation of Hsp70 both in mRNA and protein levels. No change of Hsp90, Hsp60, Hsp40 and Hsp27 were observed. Either heat shock pretreatment-induced expression of endogenous Hsp70 or overexpression of exogenous Hsp70 attenuated silibinin-induced cell apoptosis, while knocking down Hsp70 sensitized cells to apoptosis by silibinin. Silibinin-induced disruption of mitochondrial membrane potential and release of cytochrome c from mitochondria were inhibited by overexpression of Hsp70. Furthermore, silibinin inhibited the formation of complexes containing Apaf-1 and Hsp70 and increased the interaction between Apaf-1 and pro caspase-9. Additionally, the downregulation of Hsp70 by silibinin was correlated with a diminished presence of HSF1 in the nucleus, and the inhibition of transcriptional activity of HSF1. More importantly, silibinin competed with ATP for binding to the ATPase domain of Hsp70 as determined by silibinin-conjugated Sepharose pull-down assay. Consistently, either oral silibinin or intravesical instillation of silibinin suppressed the growth of xenografts in nude mice or orthotopic bladder cancer in rats respectively, which were accompanied with downregulation of Hsp70 and HSF1. CONCLUSIONS These findings firstly identify the role of Hsp70 in mediating mitochondrial apoptotic pathway induced by silibinin, and suggest selective targeting HSF1/Hsp70 signaling could produce synthetic lethality in the management of BCa. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e639-e640 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Jin Zeng More articles by this author Yule Chen More articles by this author Kaijie Wu More articles by this author Yi Sun More articles by this author Lei Li More articles by this author Dalin He More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...