The Role of the CBFB-MYH11 Complex in Leukemia Maintenance

摘要 我们实验室的长期目标是了解核心结合因子(CBF)家族在 急性髓系白血病(AML)中的转录因子CBF家族成员，其中包括RUNX1及其 结合伴侣Cbfb是白血病中最常见的突变基因。最常见的复发之一 CBF突变是由染色体倒位产生的Cbfb-MYH11(CM)融合基因 16[inv(16)]。CM的表达是AML发生发展的始动事件，但额外的协同突变， 例如激活酪氨酸激酶试剂盒中的突变，是转化为坦率白血病所必需的。厘米 被认为是在获得协同突变后也需要的，但它在白血病期间的作用 目前，人们对维护工作知之甚少。CM最初被认为主要抑制RUNX1，领先于 对肿瘤抑制基因的抑制。我们最近的工作支持一种新的融合蛋白模型 活性：CM和RUNX1共同激活白血病前基因的转录。这一新模型意味着 确定融合蛋白复合体功能上重要的靶基因可能导致新的潜在药物 目标。这个新模型的另一个扩展是CM可能需要额外的余因 转录活性。在最近的工作中，我们发现组蛋白脱乙酰酶1(HDAC1)是CM/RUNX1的一部分 复杂，是CM靶基因表达所必需的。使用inv(16)AML的小鼠模型，我们发现 在体内，HDAC1抑制剂Eninostat诱导分化，并降低白血病负担。 基于我们以前的工作，我们假设CM是促进促进基因表达所必需的 白血病的维持，而HDAC1是CM的重要辅助因素。因此，我们建议HDAC1 抑制剂将对inv(16)AML的治疗特别有用。在具体目标1中，我们将使用两个 确定CM在白血病维持中作用的补充方法：一种新的敲击小鼠模型 允许在白血病发生后删除融合基因，以及可诱导的shRNA敲除模型。 我们将使用这些工具来确定CM在体内白血病维持过程中的作用，如果CM独立的细胞 可以引起复发，并测试候选CM靶基因在白血病维持中的作用。具体而言 目的2，我们将确定CM+白血病细胞对HDAC1的需求，测试HDAC1是否影响 CM靶基因和非靶基因的表达及其与HDAC1‘S非典型性的关系 在转录激活中的作用。具体目标3将测试内抑素治疗inv(16)AML的潜力。我们 将使用遗传和患者来源的异种移植小鼠模型来测试在 标准治疗将减轻白血病负担，提高存活率。我们还将测试是否使用内抑素 联合抑制CM和达沙替尼抑制KIT中的协同突变比任何一种更有效 一个人吸毒。建议的研究是基于我们积累的经验和我们强有力的初步研究结果。 并将解决该领域的重要空白，并对inv(16)AML患者具有直接的翻译意义。

ABSTRACT The long-term goal of our lab is to understand the role of the Core Binding Factor (CBF) family of transcription factors in acute myeloid leukemia (AML). CBF family members, which include RUNX1 and its binding partner CBFB, are the most frequently mutated genes in leukemia. One of the most common recurrent CBF mutations is the fusion gene CBFB-MYH11 (CM), which is generated by of the inversion of chromosome 16 [inv(16)]. Expression of CM is the initiating event in AML development, but additional cooperating mutations, such as activating mutations in the tyrosine kinase KIT, are required for transformation to a frank leukemia. CM is assumed to also be required after the acquisition of cooperating mutations, but its role during leukemia maintenance is currently poorly understood. CM was originally thought to dominantly repress RUNX1, leading to the repression of tumor suppressor genes. Our recent work supports a new model of the fusion protein’s activity: CM and RUNX1 together activate transcription of pro-leukemic genes. This new model implies that identifying the functionally important targets genes of the fusion protein complex may lead to new potential drug targets. Another extension of this new model is that there may be additional co-factors required for CM’s transcriptional activity. In recent work, we found that Histone Deacetylase 1 (HDAC1) is part of the CM/RUNX1 complex, and is required for expression of CM target genes. Using a mouse model of inv(16) AML, we found that the HDAC1 inhibitor entinostat induced differentiation, and reduced leukemic burden in vivo. Based on our previous work, we hypothesize that CM is required for the expression of genes that promote leukemia maintenance, and that HDAC1 is an important co-factor of CM. Consequently, we propose that HDAC1 inhibitors will be particularly useful for the treatment of inv(16) AML. In Specific Aim 1, we will use two complimentary approaches to define the role of CM in leukemia maintenance: a new knockin mouse model that allows for deletion of the fusion gene after leukemia development, and an inducible shRNA knockdown model. We will use these tools to determine CM’s role during leukemia maintenance in vivo, if CM independent cells can give rise to relapse, and test the role of candidate CM target genes in leukemia maintenance. In Specific Aim 2, we will determine the requirement for HDAC1 in CM+ leukemia cells, test whether HDAC1 affects expression of both CM target and non-target genes, and test potential mechanisms for HDAC1’s non-canonical role in transcriptional activation. Specific Aim 3 will test the potential of the entinostat to treat inv(16) AML. We will use genetic and patient derived xenograft mouse models to test whether the addition of entinostat to the standard treatments will reduce leukemic burden and increase survival. We will also test whether using entinostat to inhibit CM in combination with dasatinib to inhibit cooperating mutations in KIT is more effective than either drug alone. The proposed studies are based on our accumulated experience and our strong preliminary findings, and will address important gaps in the field and have direct translational implications for inv(16) AML patients.