BET bromodomain inhibition as targeted therapy in acute myeloid leukemia

项目摘要/摘要 该项目的中心目标是了解BRD4作为急性髓系表观遗传易损性的作用。 白血病。BRD4是一个含有溴域的乙酰化转录因子和组蛋白的阅读器，是一种 一类新兴的具有转录功能的抗癌药物靶点的创始成员 助活剂。虽然早期临床试验显示BRD4抑制剂在复发难治性AML中具有活性 对于患者来说，成功地在临床上实施BRD4抑制剂仍然存在几个挑战。遵循我们的 在过去四年中，成功地揭示了BRD4上下游的作用因素 为了支持AML维护，我们现在建议解决我们对BRD4理解中的三个基本差距 作为这种疾病的表观遗传脆弱性。首先，我们寻求解决最令人困惑的问题之一 潜在的BRD4作为治疗的靶点，这与转录效应的特异性来源有关 BRD4抑制剂。在目标1中，我们将检验导致白血病的转录因子myb使用BRD4的假设 作为辅助激活剂来维持白血病细胞中的增强子景观。将定义MYB-BRD4交互 在生化和遗传水平上，并将确定这两个调控因子之间的联系是否形成 BRD4抑制剂在本病中的基因特异性效应和治疗指数的基础。一秒钟 焦点将是介体复合体，这是我们最近获得的一个30亚单位的蛋白质复合体 证明是通过BRD4在特定的顺式元件上与基因组相连。BRD4之间的紧密联系 而Mediator，以及这个超级复合体中丰富的蛋白质表面的多样性，引导我们评估 在本提案的目标2中，AML是否可能需要Mediator内的离散蛋白质模块 维护，但对于正常的生物学来说是必不可少的。这一目标将利用CRIPSR外显子扫描技术， 这是我们最近开发的，目的是探索蛋白质结构域在维持癌症中的重要性。我们期待着 新一代类似BRD4的漏洞将出现在这个综合体中，并将成为 药物发现。最后，我们试图了解并克服对BRD4抑制的获得性抗性。我们的 针对结构域的CRISPR筛选已经命名了赖氨酸脱乙酰酶SIRT6和赖氨酸甲基转移酶 SUV420H2作为调节AML细胞对BRD4抑制剂敏感性的因素。此外，我们还确定了 抑制LSD1作为克服BRD4i耐药性的策略。在目标3中，我们将确定这些组件的功能 急性髓系白血病中的调节因子及其在抑制BRD4抗白血病反应中的作用。这条大道 研究可能揭示BRD4抑制剂反应的预测性生物标记物，以及克服的潜在途径 临床上的耐药性。这项研究将继续揭示表观遗传扰动的原理 背景，这可以指导下一代治疗在这一目标类别的肿瘤学的发展。

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.