MP64-13 COMBINED N-TERMINAL ANDROGEN RECEPTOR AND AUTOPHAGY INHIBITION INCREASES THE ANTI-TUMOR EFFECT IN ENZALUTAMIDE-SENSITIVE AND ENZALUTAMIDE-RESISTANT LNCAP CELLS

Abstract

You have accessJournal of UrologyProstate Cancer: Basic Research & Pathophysiology II1 Apr 2018MP64-13 COMBINED N-TERMINAL ANDROGEN RECEPTOR AND AUTOPHAGY INHIBITION INCREASES THE ANTI-TUMOR EFFECT IN ENZALUTAMIDE-SENSITIVE AND ENZALUTAMIDE-RESISTANT LNCAP CELLS Benedikt Kranzbühler, Souzan Salemi, Tullio Sulser, and Daniel Eberli Benedikt KranzbühlerBenedikt Kranzbühler More articles by this author , Souzan SalemiSouzan Salemi More articles by this author , Tullio SulserTullio Sulser More articles by this author , and Daniel EberliDaniel Eberli More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2018.02.2058AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Multiple androgen receptor (AR) dependent and independent resistance mechanisms limit the efficacy of current castration resistant prostate cancer (CRPC) treatment. Novel N-terminal domain (NTD) binding AR targeting components including EPI-001 have the promising ability to block constitutively active splice variants; a major resistance mechanism in CRPC. Autophagy is a conserved lysosomal degradation pathway and acts as survival mechanism in cells exposed to anti-cancer treatment. We hypothesized that also a promising NTD-AR treatment may lead to up-regulation of autophagy and can be targeted by a combination treatment with autophagy inhibitors. METHODS Prostate cancer cell lines LNCaP and LNCaP-EnzR were cultured in steroid-free medium and treated with different concentrations of EPI-001 (EPI: 10, 25, 50uM) and in combination with autophagy inhibitors chloroquine (CHQ, 20uM) or 3-methyladenine (3MA, 5mM). Cell growth was assessed by WST-1-assays after 1 and 7 days. Etidium bromide and AnnexinV were used to measure viability and apoptosis on day 7 after treatment. Autophagosome increase was detected by Autodot staining. In addition, autophagic activity was monitored by western blot (WB) and immunocytochemistry for the expression of LC3-I/II, Atg5 and Beclin1. RESULTS Treatment with EPI resulted in a dose dependent reduction of cell growth and increase of apoptosis on day 7 in both cell lines. Combination of 25uM EPI with autophagy inhibitors led to a further reduction of cell viability up to 17% for CHQ, 15% for 3MA in LNCaP and up to 24% for CHQ, 36% for 3MA in LNCaP-EnzR. Assessment of autophagy levels in EPI treated cells by WB showed an increase of LC3-II and no change in Beclin1 expression in both cell lines. Immunocytochemistry detected a significant increase of Atg5 and pronounced LC3-II punctuation in EPI-001 treated LNCaP and LNCaP-EnzR. This was supported by an increase in autophagosome punctuation observed by Autodot staining. CONCLUSIONS Our data demonstrate that N-terminal androgen receptor inhibition with EPI-001 leads to increased autophagic activity in LNCaP and LNCaP-EnzR prostate cancer cells. Combination of N-terminal androgen receptor blockage with simultaneous autophagy inhibition increases the antitumor effect of EPI even in enzalutamide-resistant cells. Double treatment may offer a promising strategy to overcome resistance mechanisms in advanced prostate cancer. © 2018FiguresReferencesRelatedDetails Volume 199Issue 4SApril 2018Page: e855 Advertisement Copyright & Permissions© 2018MetricsAuthor Information Benedikt Kranzbühler More articles by this author Souzan Salemi More articles by this author Tullio Sulser More articles by this author Daniel Eberli More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...