BET bromodomain inhibition as targeted therapy in acute myeloid leukemia

项目总结/摘要 该项目的中心目标是了解BRD 4作为急性髓系白血病中表观遗传脆弱性的作用。 白血病BRD 4是乙酰化转录因子和组蛋白的含溴结构域的阅读器，并且是一种免疫抑制剂。 作为一种新兴的抗癌药物靶点的创始成员， 辅活化剂虽然早期临床试验已经揭示了BRD 4抑制剂在复发难治性AML中的活性 然而，在临床上成功实施BRD 4抑制剂仍然存在一些挑战。遵循我们 在过去四年中，在揭示BRD 4上游和下游功能因素方面的成功努力 为了支持反洗钱维护，我们现在建议解决我们在理解BRD 4方面存在的三个根本性差距 是这种疾病的表观遗传弱点首先，我们寻求解决最令人困惑的问题之一， BRD 4作为治疗靶点的基础，这与转录效应的特异性来源有关。 BRD 4抑制剂。在目的1中，我们将检验白血病转录因子MYB使用BRD 4 作为一种辅活化剂来维持白血病细胞中的增强子景观。将定义MYB-BRD 4相互作用 在生物化学和遗传水平上，并将决定这两个调节器之间的联系是否形成 BRD 4抑制剂在这种疾病中的基因特异性作用和治疗指数的基础。第二 重点领域将是介体复合物，这是一个30亚基蛋白复合物，我们最近 被证明是由BRD 4在特定的顺式元件拴在基因组上。BRD 4之间的紧密联系 和介体，以及这个超级复合体中蛋白质表面的丰富多样性，引导我们评估 在本提案的目标2中，AML是否需要Mediator内的离散蛋白模块 维持，但对正常生物学来说是不必要的。该目标将利用CRIPSR外显子扫描技术， 这是我们最近开发的一种方法，用于探测蛋白质结构域在维持癌症中的重要性。我们预计 新一代类似BRD 4的漏洞将出现在这个复杂的系统中，并将成为 药物发现。最后，我们试图了解和克服对BRD 4抑制的获得性抗性。我们 聚焦于结构域的CRISPR筛选已经提名了赖氨酸脱乙酰酶SIRT 6和赖氨酸甲基转移酶 SUV 420 H2作为调节AML细胞对BRD 4抑制剂的敏感性的因子。此外，我们还发现， LSD 1抑制作为克服BRD 4 i抗性的策略。在目标3中，我们将确定这些功能 调节因子及其在介导BRD 4抑制的抗白血病应答中的作用。这条大道 研究可能会揭示BRD 4抑制剂反应的预测生物标志物，以及克服BRD 4抑制剂反应的潜在途径。 在临床上的抵抗。这项研究将继续揭示治疗中表观遗传扰动的原理， 这可以指导肿瘤学中这一目标类别内的下一代疗法的开发。

Project Summary/Abstract The central goal of this project is to understand the role of BRD4 as an epigenetic vulnerability in acute myeloid leukemia. BRD4 is a bromodomain-containing reader of acetylated transcription factors and histones, and is a founding member of an emerging class of anti-cancer drug targets that function as transcriptional coactivators. While early stage clinical trials have revealed activity of BRD4 inhibitors in relapse-refractory AML patients, several challenges remain to successfully implement BRD4 inhibitors in the clinic. Following our successful effort over the past four years in revealing factors that function upstream and downstream of BRD4 to support AML maintenance, we now propose to address three fundamental gaps in our understanding of BRD4 as an epigenetic vulnerability in this disease. First, we seek to address one of the most perplexing issues underlying BRD4 as a therapeutic target, which is related to the source of specificity of transcriptional effects of BRD4 inhibitors. In Aim 1, we will test the hypothesis that the leukemogenic transcription factor MYB uses BRD4 as a coactivator to maintain the enhancer landscape in leukemia cells. The MYB-BRD4 interaction will be defined on a biochemical and genetic level, and will determine whether the linkage between these two regulators forms the basis for the gene-specific effects and the therapeutic index of BRD4 inhibitors in this disease. A second area of focus will be the Mediator complex, which is a 30-subunit protein complex that we have recently demonstrated is tethered to the genome by BRD4 at specific cis-elements. The intimate linkage between BRD4 and Mediator, together with the rich diversity of protein surfaces within this super-complex, leads us to evaluate in Aim 2 of this proposal whether discrete protein modules within Mediator might be required for AML maintenance, but dispensable for normal biology. This Aim will leverage the CRIPSR exon-scanning technique, which we recently developed to probe the essentiality of protein domains in sustaining cancer. We anticipate that a new generation of BRD4-like vulnerabilities will be present within this complex, and will be candidates for drug discovery. Finally, we seek to understand and overcome acquired resistance to BRD4 inhibition. Our domain-focused CRISPR screens have nominated the lysine deacetylase SIRT6 and lysine methyltransferase SUV420H2 as factors that modulate the sensitivity of AML cells to BRD4 inhibitors. In addition, we have identified LSD1 inhibition as a strategy for overcoming BRD4i resistance. In Aim 3, we will determine the function of these regulators in AML and their role in mediating the anti-leukemia response of BRD4 inhibition. This avenue of research may expose predictive biomarkers of BRD4 inhibitor responses, and potential avenues for overcoming resistance in the clinic. This research will continue to reveal principles of epigenetic perturbations in a therapeutic context, which can guide the development of next-generation therapeutics within this target class in oncology.