Cotargeting Androgen Receptor Splice Variants and MTOR Signaling Pathway for the Treatment of Castration-Resistant Prostate Cancer

Overview

Journal Clin Cancer Res

Specialty Oncology

Date 2015 Dec 30

PMID 26712685

Citations 37

Authors

Minoru Kato

Carmen A Banuelos

Yusuke Imamura

Jacky K Leung

Daniel P Caley

Jun Wang

Nasrin R Mawji

Marianne D Sadar

Affiliations

Soon will be listed here.

Abstract

Purpose: The PI3K/Akt/mTOR pathway is activated in most castration-resistant prostate cancers (CRPC). Transcriptionally active androgen receptor (AR) plays a role in the majority of CRPCs. Therefore, cotargeting full-length (FL) AR and PI3K/Akt/mTOR signaling has been proposed as a possible, more effective therapeutic approach for CRPC. However, truncated AR-splice variants (AR-V) that are constitutively active and dominant over FL-AR are associated with tumor progression and resistance mechanisms in CRPC. It is currently unknown how blocking the PI3K/Akt/mTOR pathway impacts prostate cancer driven by AR-Vs. Here, we evaluated the efficacy and mechanism of combination therapy to block mTOR activity together with EPI-002, an AR N-terminal domain (NTD) antagonist that blocks the transcriptional activities of FL-AR and AR-Vs in models of CRPC.

Experimental Design: To determine the functional roles of FL-AR, AR-Vs, and PI3K/Akt/mTOR pathways, we employed EPI-002 or enzalutamide and BEZ235 (low dose) or everolimus in human prostate cancer cells that express FL-AR or FL-AR and AR-Vs (LNCaP95). Gene expression and efficacy were examined in vitro and in vivo

Results: EPI-002 had antitumor activity in enzalutamide-resistant LNCaP95 cells that was associated with decreased expression of AR-V target genes (e.g., UBE2C). Inhibition of mTOR provided additional blockade of UBE2C expression. A combination of EPI-002 and BEZ235 decreased the growth of LNCaP95 cells in vitro and in vivo

Conclusions: Cotargeting mTOR and AR-NTD to block transcriptional activities of FL-AR and AR-Vs provided maximum antitumor efficacy in PTEN-null, enzalutamide-resistant CRPC. Clin Cancer Res; 22(11); 2744-54. ©2015 AACR.

Citing Articles

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