BET degraders for improving colorectal cancer therapy

项目总结/摘要 结直肠癌（CRC）是美国癌症相关死亡的主要原因之一。开发新型 更有效的CRC治疗是一个未满足的生物医学需求，因为大多数晚期和转移性CRC， 初始治疗后的进展对治疗性治疗反应不佳。布罗莫结构域和额外末端 结构域（BET）家族蛋白如BRD 4是控制关键致癌基因表达的表观遗传阅读器， 蛋白质驱动CRC启动和进展。使用小分子靶向BET家族蛋白 抑制剂已经成为一种有前途的治疗方法。然而，BET抑制剂（BETi）作为单一药剂 通常对包括CRC在内的上皮癌无效。的分子机制 BET靶向剂的抗癌活性还没有被很好地理解。最近，一类新的诱导剂， 已经开发了BET蛋白质的快速降解。我们的初步研究表明，两个这样的BET 降解剂（BETd），BETd 260和BETd 246，在CRC细胞中比其他BET靶向剂有效得多 和患者来源的异种移植物（PDX）。我们确定了一种新的，对目标的作用机制，BETd在 转录激活死亡受体5（DR 5），其是外源性凋亡途径的关键组分。 重要的是，DR 5的诱导对于BETd的细胞杀伤和化学增敏作用是必不可少的， 在斑点型POZ中具有激活突变的CRC亚组中负责增加BETd敏感性 蛋白（SPOP），BET蛋白的E3泛素连接酶的亚基。此外，我们的数据表明， 通过诱导DR 5介导的免疫原性细胞死亡（ICD）产生强大的免疫原性作用。的组合 BETd 260和抗PD-1抗体耐受性良好，并且几乎根除了小鼠CT 26同源肿瘤。 DR 5依赖性方式。基于这些发现，我们假设BETd通过以下方式改善CRC治疗： 诱导DR 5介导的CRC细胞杀伤和抗肿瘤免疫。目标1.确定机制和生物标志物 BETd在CRC细胞中的有效抗癌活性;目的2.确定BETd对以下疾病的治疗效果： 难治性和转移性CRC;目的3.描述和利用BETd的免疫原性作用， 改善CRC疗法。预计拟议的研究将提供新的机制见解，并建立 使用BETd开发精确和个性化治疗的关键临床前参数， 难治性和不可治愈的CRCs。从长远来看，这些研究可能会导致新的和改进的疗法 针对CRCs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.