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总体和亚组特异性表观遗传学改变。最近的研究已经确定了已知和推定的表观遗传修饰剂中的体细胞突变，包括TET 2，其编码一种将羟基添加到5-甲基胞嘧啶并导致随后DNA低甲基化的酶。重要的是，TET 2突变在AML中复发，并与不良结局相关。这些研究提出了TET 2和表观遗传修饰剂中的其他突变通过造血细胞中表观遗传状态的失调而促进造血转化的可能性。我们假设，有遗传和表观遗传改变影响主调控的表观遗传状态，这些特定的改变影响造血转化通过离散修改特定靶基因的表观遗传状态。我们认为TET 2就是这样一个表观遗传调节因子。我们将评估TET 2突变在原发性AML样本研究和我们的新的TET 2条件性敲除模型中在AML发病机制中的作用，该模型涉及TET 2在干细胞自我更新和骨髓转化中的作用。本提案的具体目的是：1）使用最先进的下一代测序技术评估突变TET 2对正常/恶性干细胞/祖细胞中表观遗传状态和基因表达的影响。我们还将2）评估TET 2缺失对体内骨髓转化的影响，并开发新的TET 2依赖性AML模型用于生物学和治疗研究。最后，鉴于我们的初步数据表明TET 2突变与不良结局和复发率增加相关，我们将3）研究TET 2突变AML对化疗反应不良的基础，并测试细胞毒性/表观遗传学联合治疗作为该基因定义的AML子集的替代治疗策略。

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.