Determining the Role of BCOR Mutations in Myeloid Malignancies

 描述(申请人提供)：急性髓系白血病(AML)是一种遗传异质性的骨髓癌，每年在美国至少影响15,000人，并导致显著的发病率和死亡率。我们在一组基因中发现了BCOR功能缺失突变，这些基因在急性髓细胞白血病中发生特殊突变，出现在骨髓增生异常综合征之后，在老年患者中很常见，并与不良的临床结果有关。BCOR突变驱动白血病发生的机制尚不清楚。在初步研究中，我们表明BCOR突变促进了造血干细胞的自我更新，并使原代细胞对激活RAS突变敏感。这是首次报道的BCOR缺陷性髓系疾病的小鼠模型。我们还首次证明了BCOR蛋白在人AML细胞系中与一个变异的多梳抑制复合体1(PRC1)的成分相互作用，这表明泛素化的组蛋白2A赖氨酸119(H2AK119ub)在AML的发展中具有重要的功能。我们的假设是，影响BCOR的体细胞突变导致无法通过还原H2AK119ub将PRC2招募到多梳抑制靶点。为了明确BCOR在髓系恶性肿瘤发生和发展过程中功能的分子基础，我们提出了以下具体目标：1)确定BCOR缺失对原代TET2-/-造血细胞髓系转化的贡献。我们将利用CRISPR/Cas9基因在体外和体内对原代小鼠TET2/-细胞进行编辑，以确定BCOR功能缺失突变对造血干细胞自我更新和谱系特异性分化的功能影响。2)确定RAS突变在促进BCOR缺陷细胞转化中的作用。我们将利用新的体外和体内模型来确定在BCOR缺陷细胞转化过程中激活RAS突变的协同效应。3)明确BCOR缺陷对髓系白血病发生过程中组蛋白表观遗传修饰的影响。我们将确定BCOR缺失对人类AML细胞系中组蛋白H3表观遗传标记的全局和位点特异性影响，并评估EZH2的遗传和化学靶向是否减弱BCOR相关的转化。总的来说，从这些研究中获得的信息将为AML的生物学提供新的见解，并为开发新的靶向治疗奠定基础。申请者科尔曼·林德斯利博士概述了一项为期五年的职业发展计划，以实现他成为转化性白血病研究的独立研究员的目标。林德斯利博士组建了一个由国际公认的专家组成的咨询委员会，提供科学和职业指导。他与癌症表观遗传学、白血病遗传学和应用生物统计学方面的专家建立了合作关系，以提供该领域的实验建议和具体培训。达纳-法伯癌症研究所是完成林德斯利博士科学和职业目标的最佳环境，因为它拥有杰出的研究团体和培养独立内科科学家的长期记录。

 DESCRIPTION (provided by applicant): Acute myeloid leukemia (AML) is a genetically heterogeneous bone marrow cancer affecting at least 15,000 individuals per year in the US and causing significant morbidity and mortality. We identified BCOR loss of function mutations among a set of genes that is specifically mutated in AML that arises after myelodysplastic syndromes, is common among older patients, and is associated with poor clinical outcomes. The mechanisms by which BCOR mutations drive leukemogenesis are not understood. In preliminary studies, we showed that Bcor mutations promote increased hematopoietic stem cell self-renewal and sensitize primary cells to activating RAS mutations. These represent the first reported mouse models of Bcor-deficient myeloid disease. We also demonstrate for the first time that BCOR protein interacts in human AML cell lines with components of a variant polycomb repressive complex 1 (PRC1), suggesting a functional importance of ubiquinated histone 2A lysine 119 (H2AK119ub) in AML development. Our hypothesis is that somatic mutations affecting BCOR cause failure to recruit PRC2 to polycomb repressive targets via reduction of H2AK119ub. To define the molecular basis of BCOR function during initiation and progression of myeloid malignancies, we propose the following Specific Aims 1) Define the contribution of Bcor deletion to myeloid transformation in primary Tet2-/- hematopoietic cells. We will use CRISPR/Cas9 gene editing in primary mouse Tet2-/- cells in vitro and in vivo to define the functional impact of Bcor loss of function mutations on hematopoietic stem cell self-renewal and lineage-specific differentiation. 2) Identify the role of RAS mutations in promoting transformation of Bcor- deficient cells. We will take advantage of novel in vitro and in vivo models to identify the cooperative effects of activating RAS mutations during transformation of Bcor-deficient cells. 3) Define the impact of BCOR deficiency on histone epigenetic modifications during myeloid leukemogenesis. We will define the global and locus-specific effects of BCOR deletion on histone H3 epigenetic marks in a human AML cell line and assess whether genetic and chemical targeting of EZH2 attenuates BCOR-associated transformation. Collectively, the information learned in these studies will provide new insights into the biology o AML and lay the groundwork for developing novel targeted therapies. The applicant, Dr. Coleman Lindsley, has outlined a five-year career development plan to meet his goal of becoming an independent investigator in translational leukemia research. Dr. Lindsley has assembled an Advisory Committee of internationally recognized experts to provide scientific and career mentorship. He has established collaborations with experts in cancer epigenetics, leukemia genetics, and applied biostatistics to provide experimental advice and specific training in the field. Dana-Farber Cancer Institute is an optimal environment for completion of Dr. Lindsley's scientific and career goals, given its outstanding research community and long-standing record for training independent physician-scientist.