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Identification and characterization of androgen receptor splice variants preferred bindings that drive prostate cancer progression [ChIP-seq]

ABSTRACT: Androgen receptor (AR) splice variants (ARVs) are implicated in developing castration-resistant (CR) prostate cancer (CRPC). Little is known about the ARV-mediated transcription program in CRPC. We identified ARV-preferred binding sites (ARV-PBS) and unique transcriptome in CRPC cells. ARVs preferentially bind to enhancers located in nucleosome-depleted regions with the full AR-response element (AREfull), while full-length AR (ARFL)-PBS are enhancers resided in closed chromatin regions with the composite FOXA1-nnnn-AREhalf motif. ARV-PBS exclusively overlapped with AR binding sites in CR patients. ARV-driven genes were up-regulated in abiraterone-resistant patient specimens and promote CRPC growth. We uncover distinct genomic and epigenomic characteristics of ARV-PBS and a unique ARV-dependent transcriptional program that not only drives CR progression but could also offer new targets for therapy. Increasing evidence suggests a pivotal role of ARVs in the acquisition of anti-AR therapy resistance in CRPC. It has been shown previously that ARVs possess unique structural and functional features such as completely lacking or only containing an impaired ligand-binding domain but constitutively active. Our findings advance the understanding of ARVs by demonstrating that ARV-PBS exhibit distinctive DNA-binding motif, GC content, and nucleosome and epigenetic characteristics. We further unravel that ARV-PBS exclusively overlap with AR bindings identified from castration-resistant patients and ARV activity is significantly increased in abiraterone-resistant patients. Given that there is no drug available to target ARVs at present, identification of ARV-mediated unique downstream pathways opens new avenues for the development of effective therapeutics for CRPC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE80742 | GEO | 2018/03/07

REPOSITORIES: GEO

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Project description:Continued androgen receptor (AR) signaling is an established mechanism underlying castration-resistant prostate cancer (CRPC), and suppression of AR signaling remains a therapeutic goal of CRPC therapy. Constitutively active androgen receptor splicing variants (AR-Vs) lack the AR ligand-binding domain (AR-LBD), the intended target of androgen deprivation therapies (ADT) including new CRPC therapies such as abiraterone and MDV3100. While the canonical full-length AR (AR-FL) and AR-Vs are both increased in CRPC, their expression regulation, associated transcriptional programs, functional relationships, and respective roles in mediating responses to endocrine therapies have not been dissected. In this study, we show that suppression of canonical AR-FL signaling by targeting AR-LBD leads to increased AR-V expression in two cell line models of CRPC. Importantly, treatment-induced AR-Vs activate a distinct expression signature enriched for cell cycle genes without requiring the presence of AR-FL. Conversely, activation of AR-FL signaling suppresses the AR-V signature but activates expression programs mainly associated with macromolecular synthesis, metabolism, and differentiation. In prostate cancer cells and CRPC xenografts treated with MDV3100 and abiraterone, increased expression of two constitutively active AR-Vs, AR-V7 and ARV567ES, but not AR-FL, parallels increased expression of the AR-driven cell cycle gene UBE2C. In addition, protein expression of AR-V7, but not AR-FL, is positively correlated with UBE2C in clinical CRPC specimens. The cumulative in vitro and in vivo evidence support an adaptive shift toward AR-V-mediated signaling in at least a subset of CRPC tumors as the AR-LBD is rendered inactive, suggesting an important mechanism contributing to drug resistance to CRPC therapies. LNCaP cells lacking AR-V were transfected with AR-V7 with or without androgen stimulation of AR-FL (4 conditions); LNCaP95 cells expressing AR-Vs were treated with control siRNA or siRNA trageting AR-LBD or AR-DBD, with or without androgen stimulation of AR-FL (6 conditions); VCaP cells expressing AR-Vs in the presence of androgen were treated with control siRNA, siRNA trageting AR-LBD, DMSO or MDV3100 to inhibit AR-FL (4 conditions). Total 14 arrays with no replicates.

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Identification and characterization of androgen receptor splice variants preferred bindings that drive prostate cancer progression [ChIP-seq]

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