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ARv7 represses tumor suppressors genes in castration-resistant prostate cancer [ChIP-Seq]

ABSTRACT: Endocrine therapies in prostate cancer (PCa) treatment block androgen receptor (AR) function, but are palliative as tumors progress to a lethal, castration-resistant state (CRPC). CRPC remains dependent on AR signaling, which can act through the full-length AR (ARfl) or constitutively active splice variants, e.g. ARv7. We show here that both ARfl and ARv7 bind to the same genomic region and heterodimerize in a CRPC cell line model, but regulate distinct transcriptomes. ARv7, unlike ARfl, preferentially represses transcription and demonstrates an increased affinity for co-repressors, decreased chromatin residence time and lower dependence on FOXA1 binding. We identified a group of ARv7-repressed genes, including the UDP-galactosyltransferase B4GALT1 that are down-regulated during PCa progression and important for CRPC growth. In conclusion, we propose that ARv7 acts as a transcriptional repressor of genes that limit proliferation, a function that should be targeted in CRPC patients.

ORGANISM(S): Homo sapiens

PROVIDER: GSE106559 | GEO | 2018/11/02

REPOSITORIES: GEO

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Project description:Enzalutamide (ENZ) is a potent androgen receptor (AR) antagonist with activity in castration-resistant prostate cancer (CRPC); however, progression to ENZ-resistant (ENZ-R) CRPC frequently occurs with rising serum PSA levels, implicating AR full length (ARFL) or variants (AR-Vs) in disease progression. To define functional roles of ARFL and AR-Vs in ENZ-R CRPC, we designed 3 antisense oligonucleotides (ASO) targeting exon 1, intron 1, and exon 8 in AR pre-mRNA to knockdown either ARFL alone, or ARFL plus AR-Vs, and examined their respective effects in LNCaP-derived ENZ-R, as well as M12 and 22Rv1, cells. ENZ-R LNCaP xenografts express high levels of both ARFL and AR-V7 compared to CRPC LNCaP xenografts. In particular, ARFL levels were ~20-fold higher than AR-V7. ENZ-R LNCaP sub-lines, derived by selection from the ENZ xenografts, also expressed uniformly high levels of ARFL and AR-V7 compared to CRPC LNCaP cells. In addition, both ARFL and AR-V7 are highly expressed in the nuclear fractions of ENZ-R-LNCaP. In ENZ-R LNCaP cells, knockdown of ARFL alone, or ARFL plus AR-Vs, similarly induced apoptosis, suppressed cell growth and AR-regulated gene expression in vitro, and delayed tumour growth in vivo. In 22Rv1 cells that are inherently resistant to ENZ, knockdown of both ARFL and AR-Vs more potently suppressed cell growth, AR transcriptional activity and AR-regulated gene expression than knockdown of ARFL alone. These data indicate the AR is an important driver of ENZ resistance, and while the contributions of ARFL and AR-Vs can vary across cell systems, ARFL is the key driver in the ENZ-R LNCaP model. AR targeting strategies against both ARFL and AR-Vs is a rational approach for AR-dependent CRPC. CRPC and ENZ-R LNCaP xenografts were generated as described in: Gleave, M.E., et al., Serum prostate specific antigen levels in mice bearing human prostate LNCaP tumors are determined by tumor volume and endocrine and growth factors. Cancer Res, 1992. 52(6): p. 1598-605.

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ARv7 represses tumor suppressors genes in castration-resistant prostate cancer [ChIP-Seq]

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