MP24-14 METABOLIC SHIFT UNDER HYPOXIC ENVIRONMENT CAUSES RESISTANCE TO MTOR INHIBITOR IN HUMAN CASTRATION RESISTANT PROSTATE CANCER.

Abstract

You have accessJournal of UrologyProstate Cancer: Basic Research I1 Apr 2014MP24-14 METABOLIC SHIFT UNDER HYPOXIC ENVIRONMENT CAUSES RESISTANCE TO MTOR INHIBITOR IN HUMAN CASTRATION RESISTANT PROSTATE CANCER. Yota Yasumizu, Takeo Kosaka, Yasumasa Miyazaki, Eiji Kikuchi, Akira Miyajima, and Mototsugu Oya Yota YasumizuYota Yasumizu More articles by this author , Takeo KosakaTakeo Kosaka More articles by this author , Yasumasa MiyazakiYasumasa Miyazaki More articles by this author , Eiji KikuchiEiji Kikuchi More articles by this author , Akira MiyajimaAkira Miyajima More articles by this author , and Mototsugu OyaMototsugu Oya More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2014.02.295AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Microenvironmental regulation of PI3K/Akt/mTOR signaling pathways and the efficacy of PI3K/mTOR inhibitors in hypoxic conditions have not been fully characterized yet. Recently we demonstrated that the activated PI3K/Akt/mTOR signaling pathway induced by androgen deprivation therapy or docetaxel explains in part the aggressiveness of castration resistant prostate cancer (CRPC). The aim of this study was to explore the efficacy of a dual PI3K and mTOR inhibitor and mTOR inhibitor for docetaxel resistant CRPC under hypoxia. METHODS Human CRPC cell lines: C4-2 and C4-2AT6 cell lines were used in this study. The C4-2AT6 cell line was established from C4-2 cells grown in androgen ablated serum for six months. We examined the changes in PI3K/Akt/mTOR pathway and hypoxia-related proteins under hypoxic conditions by using the dual PI3K and mTOR inhibitor NVP-BEZ235, and the mTOR inhibitor everolimus. RESULTS We investigated the expression of phosphorylated status in PI3K/Akt/mTOR pathway, HIF-1a, and pyruvate kinase isoform M2 (PKM2) in C4-2 and C4-2AT6 cells cultured under normoxia or hypoxia. PKM2 inactivates conversion of phosphoenolpyruvate to pyruvate and contributes to a metabolic shift that is required to cope with a hypoxic environment. Although under normoxia C4-2 and C4-2AT6 cells expressed elevated phosphorylated Akt (pAkt), phosphorylated S6 (pS6) and PKM2, a 5% hypoxic environment further induced expression of these proteins. These results indicate the PI3K/Akt/mTOR pathway is induced under hypoxic conditions. Next, we examined the cytotoxic effect of NVP-BEZ235 and everolimus under hypoxia by direct cell count. The relative cell number for treatment with 500nM NVP-BEZ235 and 100nM everolimus under 5% hypoxia compared to control was 0.46 ± 0.04 and 0.91 ± 0.11, respectively, while the relative cell number for treatment with the same doses of these drugs under normoxia was 0.47 ± 0.05 and 0.68 ± 0.08, respectively. NVP-BEZ235 showed a cytotoxic effect under hypoxia as well as normoxia (p<0.01). However, everolimus showed little cytotoxic effect under hypoxia. Western blot analysis revealed NVP-BEZ235 inhibited the expression of pAkt, pS6 and PKM2 in a dose-dependent manner. Everolimus did not inhibit the expression of pAkt or PKM2, although pS6 was fully inhibited. These results suggest that up-regulation of PKM2 is one possible mechanism of resistance to mTOR inhibitors in CRPC. CONCLUSIONS A hypoxic microenvironment modulates the sensitivity of mTOR inhibitors through PKM2 expression. © 2014FiguresReferencesRelatedDetails Volume 191Issue 4SApril 2014Page: e264 Advertisement Copyright & Permissions© 2014MetricsAuthor Information Yota Yasumizu More articles by this author Takeo Kosaka More articles by this author Yasumasa Miyazaki More articles by this author Eiji Kikuchi More articles by this author Akira Miyajima More articles by this author Mototsugu Oya More articles by this author Expand All Advertisement Advertisement PDF DownloadLoading ...