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An unorthodox AR addiction drives enzalutamide resistance in prostate cancer (ChIP-Seq)

ABSTRACT: Acquisition of resistance to the next-generation anti-androgen enzalutamide (ENZ) constitutes a major challenge for the treatment of castrate-resistant prostate cancer (CRPC). Most ENZ-resistant (ENZ-R) CRPCs are androgen receptor (AR)-positive (CRPCAR+), but often negative for prostate-specific antigen (PSA), a well-established surrogate of AR activity, implying the emergence of AR-indifferent disease. Through genome-wide ChIP-seq and RNA-seq profiling in disease-relevant ENZ-R CRPCAR+ cells, we identified a unique set of gained AR binding sites (ARBS-G) lacking the canonical DNA binding elements of AR and the pioneer factor FOXA1. ARBS-G loci are highly enriched with CpG islands and significantly overlapped with the binding sites of the unmethylated CpG dinucleotide-binding protein CXXC5 and the partner TET2. Expression of CXXC5 and its downstream targets including inhibitor of differentiation-1 (ID1) was upregulated in ENZ-R CRPCAR+ cell lines, patient-derived xenografts (PDXs) and patient specimens. Genetic depletion of AR, CXXC5 or ID1 restored ENZ sensitivity in human ENZ-R CRPCAR+ cells. Most importantly, ENZ-R CRPCAR+ cells, organoids, xenografts and PDXs were invariably hypersensitive to the novel BET-CBP/p300 dual inhibitor NEO2734. These results reveal that ENZ-R CRPCAR+ cancers are only indifferent to the canonical AR (cAR) activity, but remain addictive to the noncanonical AR (ncAR) function which is selectively vulnerable upon dual inhibition of CBP/p300 and BET family proteins.

ORGANISM(S): Homo sapiens

PROVIDER: GSE136128 | GEO | 2020/08/20

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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An unorthodox AR addiction drives enzalutamide resistance in prostate cancer (ChIP-Seq)

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