Abstract 3046: Identification of lncRNAs involved in regulation of androgen receptor splice variants in prostate cancer through CRISPR-Cas9-based screen

Abstract

Abstract Prostate cancer is the second leading cause of death in men in the USA. Despite the high initial response rates to androgen deprivation therapy (ADT), these tumors ultimately develop the resistance, i.e., castration-resistant prostate cancer (CRPC). One of the contributing factors is constitutive expression of androgen receptor (AR) splice variants such as AR3, a major splice variant identified in clinical specimens. However, little is known about long non-coding RNAs (lncRNAs) on regulation of AR splicing. In this study, we generate CRISPR/Cas9-based libraries against a focus group of lncRNAs and an AR3 mini-gene reporter to identify lncRNAs involved in regulation of AR splicing. The principles of this screening system is that only sgRNAs capable of promoting AR3 expression will be enriched in SAM (Synergistic Activation Mediator) library, whereas these clones are lost from the knockout gRNA library after selection. This screen identifies several candidate lncRNA sgRNAs and dual gRNAs (targeting Lnc-DC/ Har1B/ LINC00568/ DHRS4-AS1/ SNHG5). Further characterization confirms the regulation of their corresponding endogenous genes and AR3 expression. Importantly, overexpression of Lnc-DC increases AR3 level and enhances tumor cell growth in response to androgen deprivation. Moreover, while ectopic expression of DHRS4-AS1 increases, DHRS4-AS1 knockout suppresses AR3. Finally, rescue experiments restore the ability of DHRS4-AS1 to induce AR3, further supporting a role for Lnc-DC and DHRS4-AS1 in AR3 regulation. Together, we demonstrate that the CRISPR/Cas9-based screening system provides a powerful tool for lncRNA research. As a result, these lncRNAs may serve as biomarkers to predict the response to ADT or therapeutic targets for treatment of CRPC. Citation Format: Tsui-Ting Ho, Pratirodh Koirala, Nanjiang Zhou, Yin-Yuan Mo. Identification of lncRNAs involved in regulation of androgen receptor splice variants in prostate cancer through CRISPR-Cas9-based screen [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3046. doi:10.1158/1538-7445.AM2017-3046