CBP Bromodomain Antagonists Block Androgen Receptor in Prostate Cancer

描述（由申请人提供）： 前列腺癌（PCa）仍然是男性死亡的主要原因。雄激素受体（AR）在前列腺的正常发育过程中起着重要作用，并调节前列腺癌细胞的增殖、分化和凋亡。因此，由于这种器官特异性，AR仍然是有价值的治疗靶点。虽然已知CBP/p300（CREB结合蛋白）介导的AR赖氨酸乙酰化（ARKac）在前列腺细胞中AR激活和下游靶基因控制中起重要作用，但ARKac之后的分子事件仍不清楚。我们的研究阐明了遗传毒性应激后CBP介导的p53赖氨酸382（p53 Kac 382）乙酰化的分子事件的机制细节。我们发现CBP通过其布罗莫结构域（CBP BRD）被招募到p53 K382 ac部分：一种特异性分子相互作用，对于参与G1细胞周期阻滞的细胞周期蛋白依赖性激酶抑制剂p21的p53诱导的转录激活至关重要。初步数据显示，CBP BRD的小分子抑制剂（SMI）通过下调LNCaP和PC 3细胞中的前列腺特异性抗原（PSA）来抑制AR表达和转录活性。在这里，我们假设CBP BRD在ARKac介导的靶基因调控和细胞命运决定中发挥关键作用;因此，CBP BRD的高选择性SMI可以改变癌细胞凋亡的命运。因此，本研究计划的长期目标是阻断PCa中的AR功能。虽然已经报道了AR中的多个乙酰化位点，但这些赖氨酸残基的单独或组合乙酰化对AR活性的具体影响仍有待澄清。此外，尽管AR是序列特异性DNA结合转录因子，但染色质上的PTM以及AR在调节下游基因中的作用是未知的。提出了一种多方面的方法来解决AR转录激活的机制基础作为乙酰化的结果。为实现这一目标，提出了两个具体目标：（1）验证CBP BRD作为PCa的新治疗靶点;（2）分析伴随整体染色质和AR靶基因PSA表观遗传学变化的细胞反应。从拟议的研究中出现的结果，预计将提高我们的AR功能的分子基础的理解。鉴于AR在PCa中的核心作用，这些研究将对人类肿瘤的预后和治疗产生重要影响。

DESCRIPTION (provided by applicant): Prostate cancer (PCa) remains a leading cause of death in men. Androgen Receptor (AR) plays a central role in normal prostate development as well as regulating cell proliferation, differentiation and apoptosis in PCa. Resultantly, AR remains a valuable therapeutic target due to this organ specificity. Although it is known that CBP/p300 (CREB binding protein) mediated lysine acetylation of AR (ARKac) plays a vital role in AR activation and control of downstream target genes in prostate cells, the molecular events that follow ARKac remains unclear. Our study elucidated the mechanistic details of molecular events that follow CBP mediated acetylation of p53 on lysine 382 (p53Kac382) upon genotoxic stress. We showed that CBP is recruited to p53K382ac moiety by its bromodomain (CBP BRD): a specific molecular interaction that is essential for p53-induced transcriptional activation of the cyclin dependent kinase inhibitor, p21, involved in G1 cell cycle arrest. Preliminary data show that a small molecule inhibitor (SMI) of CBP BRD inhibits AR expression and transcriptional activity by downregulating prostate specific antigen (PSA) in LNCaP and PC3 cells. Here, we hypothesize that CBP BRD play a key role in ARKac-mediated regulation of target genes and cell fate decisions; therefore, highly selective SMIs for CBP BRD could alter the fate of the cancer cells to apoptosis. Therefore, the long-term goal of this research plan is to block the AR function in PCa. While multiple acetylation sites in AR have been reported, the specific effects of individual or combined acetylation of these lysine residues on AR activity remains to be clarified. Further, despite AR being a sequence-specific DNA binding transcription factor, the role of PTMs on chromatin as well as AR in regulating downstream genes is unknown. A multifaceted approach is proposed to address mechanistic underpinnings of AR transcriptional activation as a consequence of acetylation. Two specific aims are proposed to achieve this goal: (1) validate CBP BRD as a new therapeutic target for PCa; (2) dissect cellular response concomitant with epigenetic changes on global chromatin and AR target gene PSA. The emerging results from the proposed studies are expected to enhance our understanding of the molecular basis of AR function. Given the central role of AR in PCa, these studies will have important implications for the prognosis and treatment of human tumors.