The Role of MLL-AF9 in Acute Myeloid Leukemia

MLL-AF9 在急性髓系白血病中的作用

• 批准号: 7698026
• 负责人: JAMES C MULLOY
• 金额: $ 37.09万
• 依托单位: CINCINNATI CHILDRENS HOSP MED CTR
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-17 至 2011-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7698026
• 关键词: Acute Myelocytic Leukemia; Adhesions; Apoptosis; Biochemical; Biological Assay; Biological Models; Biology; Blood; Bone Marrow; CD34 gene; Cell Line; Cells; Chemotherapy-Oncologic Procedure; Clinic; Development; Event; Extracellular Matrix; Family; Hematopoiesis; Hematopoietic; Human; Immunodeficient Mouse; In Vitro; Induction of Apoptosis; Instruction; KITLG gene; Maintenance; Malignant Neoplasms; Measures; Modeling; Molecular; Monomeric GTP-Binding Proteins; Mus; Myeloid Cells; Oncogenes; Pathway interactions; Phenotype; Play; Protein Family; Proteins; RNA Interference; Role; Signal Pathway; Signal Transduction; Stem cells; System; Testing; Therapeutic; Therapeutic Intervention; Xenograft Model; Xenograft procedure; addiction; chemotherapy; combinatorial; human cord blood CD34+ cell; in vitro Assay; in vivo; inhibitor/antagonist; leukemia; leukemic stem cell; migration; notch protein; novel; novel therapeutic intervention; protein expression; rho; self-renewal; small hairpin RNA; standard of care

Hematopoietic as well as leukemic stem cells (HSC/LSC) are dependent on interactions with extracellular matrix, soluble factors and cellular components of the bone marrow (BM) microenvironment for their survival. These interactions are hypothesized to promote the quiescence of the stem cell and their retention in the niche and influence the decisions regarding symmetric versus asymmetric self-renewal divisions. The signals that contribute to these decisions are just now being identified and likely involve the classical molecular pathways shown to be important in stem cells, including WNT/catenin, Notch, KitL/Kit and SDF/CXCR4 signaling. Each of these signals impacts directly or indirectly on the Rho family of small GTPase proteins, including the Rac family. These proteins play an essential role in the retention of HSC in the niche and in the survival, proliferation and differentiation decisions that are critical for sustaining hematopoiesis and maintaining the integrity of the stem cell compartment. We have recently demonstrated that activated Rac is increased in a novel model of human leukemia. In this model, the MLL-AF9 (MA9) leukemia oncogene is used to transform primary human CD34+ cells and promotes a rapid acute myeloid leukemia (AML) in immunodeficient mice. Suppression of Rac-GTP formation using the Rac inhibitor NSC23766, or shRNA knockdown of Rac expression, could effectively promote apoptosis and suppress proliferation under conditions where little or no inhibitory effect could be detected on normal human CD34+ cord blood cells. The inhibition of Rac and the induction of apoptosis correlate with the loss of Bcl protein expression, especially of Bcl-xL, which is an identified downstream target of Rac2 signaling. We propose to use our newly developed leukemia model to study the role of Rac signaling in MLL leukemia cells using in vitro assays measuring well-characterized phenotypes associated with Rac activity, including migration, survival, adhesion and proliferation (Aim1). We will extend these results in vivo using a xenograft system and a pharmacologic as well as RNAi approach to inhibit Rac activity as well as Bcl-xL function (Aim 2). This combinatorial approach should enable us to determine the importance of the Rac signaling pathway in leukemia and begin to dissect the specific mechanisms involved in the Rac addiction in MA9 AML. RELEVANCE (See instructions): We have recently shown that human blood stem cells can be induced to make leukemia upon introduction

造血和白血病干细胞（HSC/LSC）取决于与细胞外基质，骨髓（BM）微环境的生存的相互作用。假设这些相互作用以促进干细胞的静止及其在利基市场中的保留，并影响有关对称性和不对称自我更新分裂的决策。现在刚刚确定了有助于这些决定的信号，并且可能涉及在干细胞中显示的经典分子途径，包括Wnt/Catenin，Notch，Kitl/kit/kit/kit和sdf/cxcr4信号传导。这些信号中的每一个都直接或间接影响小型GTPase蛋白的Rho家族，包括RAC家族。这些蛋白质在HSC在利基市场中的保留以及生存，增殖和分化决策中起着至关重要的作用，这些决策对于维持造血和维持干细胞室的完整性至关重要。我们最近证明，在人类白血病的新型模型中，激活的RAC增加了。在此模型中，MLL-AF9（MA9）白血病癌基因用于转化原代人CD34+细胞，并在免疫缺陷小鼠中促进快速的急性肌髓样白血病（AML）。使用RAC抑制剂NSC23766或RAC表达的shRNA敲低的RAC-GTP形成，可以有效地促进凋亡，并在很少或没有抑制性抑制作用的情况下对正常的人CD34+脐带血细胞抑制。 RAC的抑制作用和凋亡的诱导与BCl蛋白表达的丧失相关，尤其是BCL-XL的丧失，BCL-XL是Rac2信号传导的下游靶标。我们建议使用新开发的白血病模型使用体外测定法研究与RAC活性相关的特征良好的表型，包括迁移，生存，粘附和增殖（AIM1），研究RAC信号传导在MLL白血病细胞中的作用。我们将使用异种移植系统和药理学以及抑制RAC活性以及BCL-XL功能的RNAi方法扩展这些结果（AIM 2）。这种组合方法应该使我们能够确定白血病中RAC信号通路的重要性，并开始剖析MA9 AML中RAC成瘾所涉及的特定机制。相关性（请参阅说明）：我们最近表明，可以诱导人血干细胞引入白血病。