Role of TET2 mutations in malignant transformation and acute myeloid leukemia

描述(由申请人提供)：最近的研究已经确定了AML患者中具有生物学和预后价值的全局和亚群特异性表观遗传学改变。最近的研究已经在已知的和可能的表观遗传修饰物中发现了体细胞突变，包括TET2，它编码一种酶，将羟基添加到5-甲基胞嘧啶上，导致随后的DNA低甲基化。重要的是，TET2突变在AML中反复出现，并与不良结局相关。这些研究提出了这样一种可能性，即表观遗传修饰物中的TET2和其他突变可能通过对造血细胞表观遗传状态的失调而促进造血转化。我们假设存在影响表观遗传状态的主调控的遗传和表观遗传改变，并且这些特定的改变通过对特定靶基因的表观遗传状态的离散修改来影响造血转化。我们认为TET2就是这样一种表观遗传调控因子。我们将评估TET2突变在AML发病机制中的作用，我们将在原发AML样本和我们新的TET2条件性基因敲除模型中评估TET2在AML发病机制中的作用，该模型涉及TET2在干细胞自我更新和骨髓转化中的作用。这项提案的具体目标将1)利用最先进的下一代测序技术评估突变TET2对正常/恶性干细胞/祖细胞表观遗传状态和基因表达的影响。我们还将评估TET2缺失对体内髓系转化的影响，并开发新的、依赖TET2的AML模型，用于生物学和治疗研究。最后，鉴于我们的初步数据显示，TET2突变与不良预后和增加复发率有关，我们将3)调查TET2突变AML对化疗反应差的基础，并测试细胞毒/表观遗传联合治疗作为这一基因定义的AML亚型的替代治疗策略。

DESCRIPTION (provided by applicant): Recent studies have identified global and subset specific epigenetic alterations in AML patients with biologic and prognostic value. Recent studies have identified somatic mutations in known and putative epigenetic modifiers, including TET2, which encodes an enzyme which adds hydroxyl groups to 5-methylcytosine and leads to subsequent DNA hypomethylation. Importantly TET2 mutations are recurrent in AML and are associated with adverse outcome. These studies raise the possibility that TET2 and other mutations in epigenetic modifiers contribute to hematopoietic transformation through dysregulation of the epigenetic state in hematopoietic cells. We hypothesize that there are genetic and epigenetic alterations affecting master regulators of the epigenetic state, and that these specific alterations affect hematopoietic transformation through discrete modifications of the epigenetic state of specific target genes. We propose that TET2 is one such epigenetic regulator. We will assess the role of TET2 mutations in AML pathogenesis in studies in primary AML samples and in our novel, conditional knockout model of TET2 which implicates TET2 in stem cell self-renewal and myeloid transformation. The specific aims of this proposal will 1) assess the effects of mutant TET2 on the epigenetic state and gene expression in normal/malignant stem/progenitor cells using state-of-the-art next generation sequencing technologies. We will also 2) assess the effects of TET2 loss on myeloid transformation in vivo and develop novel, TET2-dependent AML models for biologic and therapeutic studies. Finally, given our preliminary data suggests that TET2 mutations are associated with poor outcome and increased relapse rate, we will 3) investigate the basis for the poor response of TET2-mutant AML to chemotherapy and test combination cytotoxic/epigenetic therapy as an alternate therapeutic strategy for this genetically defined subset of AML.