BET degraders for improving colorectal cancer therapy

项目摘要/摘要 结直肠癌(CRC)是美国癌症相关死亡的主要原因之一。发展中的小说 更有效的结直肠癌治疗是一个未得到满足的生物医学需求，因为大多数晚期和转移性结直肠癌 最初治疗后的进展对治疗效果不佳。溴结构域和末端外 结构域(BET)家族蛋白，如BRD4，是表观遗传阅读器，控制关键致癌基因的表达 驱动CRC启动和进展的蛋白质。利用小分子靶向BET家族蛋白 抑制剂已经成为一种很有前途的治疗方法。然而，BET抑制剂(Beti)作为单一药物 通常对包括癌在内的上皮性癌症无效。其背后的分子机制 BET靶向剂的抗癌活性还不是很清楚。最近，一类新的诱导剂 BET蛋白的快速降解已经发展起来。我们的初步研究显示，有两个这样的赌注 降解物(BETd)、BETd260和BETd246在结直肠癌细胞中比其他BET靶向剂更有效 和患者来源的异种移植物(PDX)。我们发现了BETD的一种新的靶向作用机制 转录激活死亡受体5(DR5)，这是外源性凋亡途径的关键组成部分。 重要的是，DR5的诱导对于BETD的细胞杀伤和化疗增敏作用是必不可少的，以及 斑点型POZ中具有激活突变的一组CRC对BETD敏感性的增加负责 蛋白质(SPOP)，BET蛋白E3泛素连接酶的一个亚基。此外，我们的数据表明，BETD已经 通过诱导DR5介导的免疫原性细胞死亡(ICD)产生强大的免疫原性效应。一种组合 BETd260和抗PD-1抗体耐受性良好，几乎根除了小鼠CT26同基因肿瘤 DR5依赖方式。基于这些发现，我们假设BETD通过以下方式改善CRC治疗 诱导DR5介导的CRC细胞杀伤和抗肿瘤免疫。目的1.确定发病机制和生物标志物 目的2.确定BETD对结直肠癌细胞的治疗效果 治疗--难治性和转移性癌；目标3.描述和利用BETD的免疫原性作用 改进结直肠癌治疗方法。拟议的研究有望提供新的机械性见解，并建立 使用BETD开发精确和个性化的治疗方法的关键临床前参数 治疗-难治性和不治之症。从长远来看，这些研究可能会带来新的和改进的治疗方法 对抗癌和其他类型的癌症。

PROJECT SUMMARY/ABSTRACT Colorectal cancer (CRC) is one of the leading causes of cancer-related death in the US. Developing novel and more effective CRC therapies is an unmet biomedical need as most of advanced and metastatic CRCs that progress after initial therapies respond poorly to therapeutic treatment. The bromodomain and extra-terminal domain (BET) family proteins such as BRD4 are epigenetic readers that control expression of key oncogenic proteins that drive CRC initiation and progression. Targeting the BET family proteins using small-molecule inhibitors has emerged as a promising therapeutic approach. However, BET inhibitors (BETi) as single agents are generally ineffective against epithelial cancers including CRCs. The molecular mechanisms underlying the anticancer activity of BET-targeting agents are not well understood. Recently, a new class of agents that induce rapid degradation of BET proteins has been developed. Our preliminary studies reveal that two such BET degraders (BETd), BETd260 and BETd246, are much more potent than other BET-targeting agents in CRC cells and patient-derived xenografts (PDXs). We identified a novel, on-target mechanism of action of BETd in transcriptionally activating Death Receptor 5 (DR5), a key component of the extrinsic apoptotic pathway. Importantly, the induction of DR5 is essential for the cell-killing and chemosensitization effects of BETd, and responsible for increased BETd sensitivity in a subset of CRCs with an activating mutation in Speckle-type POZ protein (SPOP), a subunit of the E3 ubiquitin ligase of BET proteins. Furthermore, our data suggest BETd have robust immunogenic effects by inducing DR5-mediated immunogenic cell death (ICD). A combination of BETd260 and anti-PD-1 antibody was well tolerated and nearly eradicated mouse CT26 syngeneic tumors in a DR5-dependent manner. Based on these findings, we hypothesize that BETd improve CRC therapies by inducing DR5-mediated CRC cell killing and antitumor immunity. Aim 1. Identify the mechanism and biomarkers of the potent anticancer activity of BETd in CRC cells; Aim 2. Determine the therapeutic efficacy of BETd against therapy-refractory and metastatic CRCs; Aim 3. Delineate and harness the immunogenic effects of BETd to improve CRC therapies. The proposed studies are expected to provide new mechanistic insights and establish key preclinical parameters for using BETd to develop precision and personalized therapies against therapy-refractory and incurable CRCs. In the long run, these studies may lead to new and improved therapies against CRCs and other types of cancer.