Abstract 5210: Darolutamide impairs prostate cancer growth by altering chromatin conformation and transcriptional activity of genes involved in cell proliferation and survival
Authors: Baumgart Simon J. , Nevedomskaya Ekaterina , Lesche Ralf , Haendler Bernard 
Published: August 2019

Abstract
Androgen signalling is essential for early and late stage prostate cancer (PCa), as demonstrated by the efficacy of androgen receptor (AR) antagonists. The AR gene and its regulatory element are frequently amplified in castration-resistant tumors for which improved treatments are highly needed. Recent findings underscore that gene regulatory elements play an important role in tumor development due to their impact on chromatin conformation and gene regulation. Here we describe the genome-wide effects of darolutamide, a novel AR antagonist which just completed a pivotal clinical phase III trial, by analyzing AR occupancy and its impact on chromatin looping, histone H3K27 acetylation and downstream gene regulation. Genome-wide RNA-seq and ChIP-seq were used to analyze the androgen-sensitive cell lines VCaP, LAPC4 and LNCaP treated with R1881, or with R1881 and darolutamide. Binding of AR and of the pioneer factor FOXA1, as well as histone H3K27 acetylation were determined. Chromatin conformation was detected using the HiChIP method with an AR-specific antibody. Differential gene expression was analyzed by DESeq2 and Gene Set Enrichment Analyses. ChIP-seq peak identification was done by MACS2. HiChIP analysis was performed with the hichipper pipeline. Darolutamide efficiently blocked AR signalling at the level of transcriptional regulation and altered chromatin landscape interaction. Analysis of transcriptomic data showed a strong reduction of the androgen response, as well as down-regulation of proliferation and cell cycle genes by darolutamide. Concordantly, AR occupancy was decreased genome-wide compared to androgen stimulation. Importantly, no binding cluster was identified which showed increased AR occupancy after darolutamide treatment, as reported for other AR antagonists. Interestingly, we observed in darolutamide-treated samples a parallel reduction of FOXA1 occupancy at AR sites, which argues for a co-dependence between this pioneer factor and the AR. Also, we found that H3K27 acetylation, a histone mark linked to active regions, was markedly down-regulated at specific enhancer and gene regions following darolutamide treatment, further pointing to reduced activity of enhancer regions recognized by the AR. Finally, determination of chromatin looping mediated by the AR between enhancers and gene promoters showed a dense network at genes involved in prostate cancer survival. The loss of AR binding at these regions was in line with the significantly reduced transcriptional response observed following darolutamide treatment. In conclusion, we found that darolutamide strongly prevented genome-wide AR binding in multiple hormone-sensitive cellular PCa models, importantly at genes involved in cell proliferation and survival. We furthermore highlight the cross-talk between the pioneer factor FOXA1 and the AR.
Citation Format: Simon J. Baumgart, Ekaterina Nevedomskaya, Ralf Lesche, Bernard Haendler. Darolutamide impairs prostate cancer growth by altering chromatin conformation and transcriptional activity of genes involved in cell proliferation and survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5210.