Novel genomic mechanism for ligand-dependent transcription by androgen receptor

雄激素受体配体依赖转录的新基因组机制 项目摘要/摘要 雄激素受体(AR)是核激素受体(NR)超家族的一员，与同源基因结合 激素反应元件(HREs)和调节内源性配体中靶基因的表达 (激动剂)-在不同组织中可诱导的方式。由于AR在前列腺癌的发生和发展中起关键作用 在癌症方面，已经开发了许多合成的AR拮抗剂来抑制内源性AR的作用 配基。一个突出的例子是苯扎鲁胺(Xtandi®)，这是一种第二代AR拮抗剂，表现出很强的 对前列腺癌具有抗癌活性。然而，对苯扎鲁胺的固有或获得性耐药性，以及所有 可用的AR拮抗剂，发生导致治疗失败。因此，目前AR的治疗效果 对抗者需要改进。拮抗剂配基AR的基因组机制研究进展 为了改进AR靶向治疗，功能是至关重要的。在初步研究中，我们已经定义了 前列腺癌中第一个高分辨(基序分辨)激动剂和拮抗剂连接的AR序列 使用一种新的染色质免疫沉淀-核酸外切酶(CHIP-EXO)方法。没想到，我们 发现AR与天然激动剂(双氢睾酮，DHT)和拮抗剂(苯扎鲁胺)结合识别 染色质上截然不同的DNA基序(称为“DNA基序转换”)。令人惊讶的是，集成芯片-exo RNA-seq分析发现，苯扎鲁胺连接的AR，结合到一个新的AR结合基序，显著 影响与癌症相关的全球转录。通过将我们新的芯片外基因组方法与其他方法相结合 表观基因组学、蛋白质组学和生物化学方法，我们进一步发现苯扎鲁胺配基的AR相互作用 与特定的协同转录因子(例如FoxA1)和非DNA结合的辅助调节因子(例如Hsp90)共同作用于 特定活跃的顺式调控区域。重要的是，药物对Hsp90的抑制显著降低 苯扎鲁胺配基的AR靶基因(如促癌基因GR和CD55)和 增强苯扎鲁胺对细胞生长的抑制作用。基于这些令人信服的数据，我们假设 DNA基序转换是拮抗剂依赖、癌症相关的一种新的基因组机制 通过拮抗剂配基的AR转录复合体转录。我们的具体目标是：1)确定是否 特定的转录因子和表观遗传特征在全球范围内促进AR DNA基序的转换；以及2) 研究拮抗剂连接的AR结合如何调节癌症相关基因的表达。显著地 加深我们对AR在基因组中如何调控拮抗剂调控转录的理解 本研究将为今后AR靶向治疗的发展奠定基础。

Novel genomic mechanism for ligand-dependent transcription by androgen receptor Project Summary/Abstract Androgen receptor (AR) is a member of nuclear hormone receptor (NR) superfamily that binds to cognate hormone responsive elements (HREs) and regulates target gene expression in an endogenous ligand (agonist)-inducible manner in diverse tissues. As AR plays a key role in the onset and progression of prostate cancer, numerous synthetic AR antagonists have been developed to inhibit the action of endogenous AR ligands. A prominent example is enzalutamide (Xtandi®), a second-generation AR antagonist showing strong anti-cancer activity for prostate cancer. However, intrinsic or acquired resistance to enzalutamide, and all available AR antagonists, occurs leading to treatment failure. Thus, therapeutic efficacy of current AR antagonists needs to be improved. Elucidation of genomic mechanisms underlying antagonist-liganded AR function is critically important in order to improve AR-targeted therapy. In preliminary studies, we have defined the first high-resolution (motif-resolution) agonist- and antagonist-liganded AR cistromes in prostate cancer cells by using a novel chromatin immunoprecipitation-exonuclease (ChIP-exo) approach. Unexpectedly, we found that AR bound to natural agonist (dihydrotestosterone, DHT) and antagonist (enzalutamide) recognizes distinctly different DNA motifs on chromatin (termed “DNA motif switching”). Surprisingly, integrated ChIP-exo and RNA-seq analysis found that enzalutamide-liganded AR, bound to a novel AR binding motif, significantly affects global, cancer-relevant transcription. By combining our novel ChIP-exo genomic approach with other epigenomic, proteomic and biochemical approaches, we further found that enzalutamide-liganded AR interacts with specific collaborating transcription factors (e.g. FoxA1) and non-DNA binding coregulators (e.g. Hsp90) on specific active cis-regulatory regions. Importantly, pharmacological Hsp90 inhibition significantly decreases expression of enzalutamide-liganded AR target genes (e.g. cancer promoting genes GR and CD55) and enhances cell growth inhibitory effect of enzalutamide. Based on these compelling data, we hypothesize that DNA motif switching is a novel genomic mechanism underlying antagonist-dependent, cancer-relevant transcription by antagonist-liganded AR transcription complex. Our specific aims are to: 1) determine whether specific transcription factors and epigenetic features globally facilitate AR DNA motif switching; and 2) investigate how antagonist-liganded AR binding regulates expression of cancer-relevant genes. By significantly enhancing our understanding of how antagonist-regulated transcription by AR is controlled at the genomic level, this study will lay the foundation for future development of improved AR-targeted therapy.