Abstract
Resistance to next-generation anti-androgen enzalutamide (ENZ) constitutes a major challenge for the treatment of castration-resistant prostate cancer (CRPC). By performing genome-wide ChIP-seq profiling in ENZ-resistant CRPC cells we identify a set of androgen receptor (AR) binding sites with increased AR binding intensity (ARBS-gained). While ARBS-gained loci lack the canonical androgen response elements (ARE) and pioneer factor FOXA1 binding motifs, they are highly enriched with CpG islands and the binding sites of unmethylated CpG dinucleotide-binding protein CXXC5 and the partner TET2. RNA-seq analysis reveals that both CXXC5 and its regulated genes including ID1 are upregulated in ENZ-resistant cell lines and these results are further confirmed in patient-derived xenografts (PDXs) and patient specimens. Consistent with the finding that ARBS-gained loci are highly enriched with H3K27ac modification, ENZ-resistant PCa cells, organoids, xenografts and PDXs are hyper-sensitive to NEO2734, a dual inhibitor of BET and CBP/p300 proteins. These results not only reveal a noncanonical AR function in acquisition of ENZ resistance, but also posit a treatment strategy to target this vulnerability in ENZ-resistant CRPC.
Highlights
Resistance to next-generation anti-androgen enzalutamide (ENZ) constitutes a major challenge for the treatment of castration-resistant prostate cancer (CRPC)
Using C4-2ENZ-R cells as a model, we further confirmed ENZ-R growth of C4-2ENZ-R cells in vivo (Supplementary Fig. 1b). Both RNA-seq and RT-quantitative PCR (qPCR) analyses showed that canonical androgen receptor (AR) target genes including KLK3 (PSA), TMPRSS2, and NKX3.1 were transcriptionally downregulated in ENZ-R cells compared to control cells (Supplementary Fig. 1c, d)
AR knockdown inhibited proliferation of ENZ-R variants of these cell lines (Supplementary Fig. 2a). These findings suggest that AR-FL is indispensable for ENZ-R growth of CRPC cells
Summary
Resistance to next-generation anti-androgen enzalutamide (ENZ) constitutes a major challenge for the treatment of castration-resistant prostate cancer (CRPC). Consistent with the finding that ARBS-gained loci are highly enriched with H3K27ac modification, ENZ-resistant PCa cells, organoids, xenografts and PDXs are hyper-sensitive to NEO2734, a dual inhibitor of BET and CBP/p300 proteins. These results reveal a noncanonical AR function in acquisition of ENZ resistance, and posit a treatment strategy to target this vulnerability in ENZ-resistant CRPC. Different mechanisms related to ENZ and ABI resistance have been identified, which include aberrant glucocorticoid receptor (GR) upregulation[9], AR splice variants (ARVs)[10,11], AR gene mutation[12], somatic acquisition of AR gene enhancers, and AR gene duplication[13,14,15]. Through genome-wide AR chromatin immunoprecipitation sequencing (ChIP-seq) and RNA sequencing (RNAseq) analyses in ENZ-resistant (ENZ-R) AR-positive CRPC cells and meta-analysis and immunohistochemistry studies in patient samples, we demonstrated a previously unrecognized noncanonical AR function in ENZ-R CPRC
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