MP04-12 PHARMACOLOGICAL INHIBITION OF THE MOLECULAR CHAPERONE HSP70 OVERCOMES BELZUTIFAN RESISTANCE IN CCRCC

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You have accessJournal of UrologyCME1 Apr 2023MP04-12 PHARMACOLOGICAL INHIBITION OF THE MOLECULAR CHAPERONE HSP70 OVERCOMES BELZUTIFAN RESISTANCE IN CCRCC Michael Basin, Sarah Backe, Michael Bratslavsky, Mark Woodford, Dimitra Bourboulia, Mehdi Mollapour, and Gennady Bratslavsky Michael BasinMichael Basin More articles by this author , Sarah BackeSarah Backe More articles by this author , Michael BratslavskyMichael Bratslavsky More articles by this author , Mark WoodfordMark Woodford More articles by this author , Dimitra BourbouliaDimitra Bourboulia More articles by this author , Mehdi MollapourMehdi Mollapour More articles by this author , and Gennady BratslavskyGennady Bratslavsky More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003215.12AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Patients with von-Hippel Lindau (VHL) mutations are predisposed to developing clear cell renal cell carcinoma (ccRCC) through constitutive activation of transcription factor hypoxia-inducible factor 2a (HIF2a). The HIF2a antagonist Belzutifan has recently been FDA approved for treatment VHL disease associated tumors. Results of the recent clinical trial (MK-4682) revealed that a certain proportion of VHL patients progress on therapy. Our objective here was to decipher the molecular mechanisms of Belzutifan mediated downregulation of HIF2a and therefore provide better understanding of drug resistance. The molecular chaperone Hsp70 promotes the stability of hundreds of client proteins, thereby protecting them from degradation. Since HIF2a interacts with Hsp70, we hypothesized that Hsp70 maintains HIF2a stability in ccRCC and is a potential alternative therapeutic target in cases of Belzutifan resistance. METHODS: Cell line models of VHL-null ccRCC (786-0, A498, 769-P) were treated with 2 mM Belzutifan. HIF2a expression levels were evaluated by immunoblotting. Wild-type (WT) or Belzutifan resistant (S304M, G323E) HIF2a were transiently expressed in 786-O cells prior to treatment with Belzutifan or an Hsp70 inhibitor (JG-98). HIF2a degradation was examined by immunoblot. RESULTS: Here, we show that HIF2a is an Hsp70 client in VHL null ccRCC cell line 786-O. Further, we demonstrated a time dependent decrease in HIF2a expression with Belzutifan (2 mM) as early as 2 hours after treatment in three VHL null ccRCC cell lines 786-0, A498, and 769-P cells. Pretreatment of ccRCC cells with the proteasome inhibitor bortezomib blocked Belzutifan mediated downregulation of HIF2a, indicating Belzutifan leads to proteasomal degradation of HIF2a through a VHL independent pathway. Utilizing previously characterized Belzutifan resistant HIF2a-S304M and -G323E mutants we demonstrated that treating ccRCC cells with Hsp70 inhibitor JG-98 leads to mutant-HIF2a degradation, therefore overcoming Belzutifan resistance. CONCLUSIONS: The FDA-approved HIF2a inhibitor Belzutifan causes proteasomal degradation of WT-HIF2a, but not of resistant mutants. Our data indicates that HIF2a stability is reliant on the molecular chaperone Hsp70. Further, treatment with an Hsp70 inhibitor could potentially be used in the clinic to overcome resistance to Belzutifan in patients with VHL disease and ccRCC. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e37 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Michael Basin More articles by this author Sarah Backe More articles by this author Michael Bratslavsky More articles by this author Mark Woodford More articles by this author Dimitra Bourboulia More articles by this author Mehdi Mollapour More articles by this author Gennady Bratslavsky More articles by this author Expand All Advertisement PDF downloadLoading ...