Molecular Pathogenesis of Acute Myeloid Leukemia

 描述（由申请人提供）：在本提案中，我们将试图确定急性髓性白血病（AML）起始突变作用的精确分子机制，并在治疗上利用这些机制。绝大多数患有AML的患者仍然死于他们的疾病。迫切需要更有效、毒性更小的新疗法。最近的AML基因组测序研究告诉我们，几乎所有的AML肿瘤都是克隆异质性的。每个肿瘤都起源于一个创始克隆，该克隆是由一个起始突变产生的，该突变允许单个造血干/祖细胞（HSPC）实现克隆优势。这种“白血病前期”克隆获得了额外的协同突变，导致了基础克隆的发展和临床上明显的AML。子克隆从创建克隆产生，也可以从其他子克隆进化而来。无论如何，所有的亚克隆都含有基础克隆突变。虽然协同突变通常对靶向治疗（例如FLT 3和/或IDH 1/2抑制剂）有吸引力，但它们有时存在于亚克隆中（即它们仅存在于总白血病细胞群的一部分中）;不能预期亚克隆的治疗靶向是治愈性的。这项工作的中心假设是，要完全理解AML的发病机制，就必须完全理解启动突变的后果。我们还假设针对起始突变的治疗方法最有可能为AML患者提供长期益处。我们将充分表征两种常见的、经过充分验证的AML起始突变（PML-RARA和DNMT 3A R882 H），这两种突变都与造血细胞中深刻的表观遗传学改变相关。我们将利用最先进的技术（包括大RNA和小RNA的综合性，链特异性RNA-seq，全基因组亚硫酸氢盐测序，染色质可及性研究以及癌基因结合和组蛋白修饰的ChIP-seq研究）来确定这些起始突变的关键基因组靶点，以及无偏见的蛋白质组学技术来全面鉴定与突变蛋白特异性相互作用的蛋白质。我们将整合这些数据，以确定基因，RNA，基因座和途径，改变了由启动 突变，并开发关于可能与AML发病机制相关的机制的新假设。我们将在人胚胎干细胞和表达PML-RARA或DNMT 3A R882 H的转基因小鼠中模拟AML起始突变和下游通路，以充分探索通路（例如DNA甲基化和/或组蛋白修饰剂）和/或可能对其作用至关重要的协同突变的贡献。作为本工作的转化目标，我们将尝试开发一种新型药物，其将抑制突变体DNMT 3A R882 H蛋白的作用，该突变体DNMT 3A R882 H蛋白充当WT DNMT 3A的显性负性抑制剂，从而抑制HSPC中的从头DNA甲基化。该突变引起局部典型DNA低甲基化，这是一种可被有效抑制剂逆转的事件，可恢复正常HSPC功能。

 DESCRIPTION (provided by applicant): In this proposal, we will attempt to determine the precise molecular mechanisms by which acute myeloid leukemia (AML)-initiating mutations act, and to exploit these mechanisms therapeutically. The vast majority of patients who develop AML still die from their disease. New therapies that are more efficacious and less toxic are urgently needed. Recent AML genome sequencing studies have taught us that virtually all AML tumors are clonally heterogeneous. Each tumor originates from a founding clone that was created by an initiating mutation that allowed a single hematopoietic stem/progenitor cell (HSPC) to achieve a clonal advantage. This `preleukemic' clone acquires additional, cooperating mutations that lead to the development of a founding clone, and clinically apparent AML. Subclones arise from the founding clone, or can evolve from other subclones. Regardless, all subclones contain the founding clone mutations. Although cooperating mutations are often attractive for targeted therapies (e.g. FLT3 and/or IDH1/2 inhibitors), they are sometimes found in subclones (i.e. they are only in a fraction of the total leukemic cell population); therapeutic targeting of subclones cannot be expected to be curative. The central hypothesis of this work is that a complete understanding of the consequences of initiating mutations is required to fully understand AML pathogenesis. We also hypothesize that therapeutic approaches directed against initiating mutations are the most likely to provide long-term benefit for AML patients. We will fully characterize two common, well-validated AML-initiating mutations (PML-RARA and DNMT3A R882H) that are both associated with profound epigenetic alterations in hematopoietic cells. We will utilize state-of-the-art techniques (including comprehensive, strand-specific RNA-seq of large and small RNAs, whole genome bisulfite sequencing, chromatin accessibility studies, and ChIP-seq studies for oncogene binding and histone modifications) to pinpoint the key genomic targets of these initiating mutations, and unbiased proteomic techniques to comprehensively identify proteins that interact specifically with the mutant proteins. We will integrate these data to identify genes, RNAs, loci, and pathways that are altered by the initiating mutations, and develop new hypotheses regarding mechanisms that may be relevant for AML pathogenesis. We will model AML-initiating mutations and downstream pathways both in human embryonic stem cells, and in transgenic mice expressing PML-RARA or DNMT3A R882H, to fully explore the contributions of pathways (e.g. DNA methylation and/or histone modifiers) and/or cooperating mutations that may be critical for their actions. As a translational goal of thi work, we will attempt to develop a novel drug that will inhibit the action of the mutant DNMT3A R882H protein, which acts as a dominant negative inhibitor of WT DNMT3A, thereby suppressing de novo DNA methylation in HSPCs. This mutation causes in focal, canonical, DNA hypomethylation, an event that may be reversed by an effective inhibitor, which may restore normal HSPC function.