Targeting Cdc42 in leukemia stem cells

摘要 该项目的目标是使用遗传手段来证明Rho GT3， Cdc 42是白血病干细胞（LSC）的一个新靶点， 用于抑制人血液中失调的Cdc 42活性的Cdc 42药理学抑制剂 干细胞恶性肿瘤Cdc 42信号轴位于许多信号传导的十字路口， 事件和Cdc 42与其许多相关效应子之间的功能相互作用 介导多种生理反应，包括肌动蛋白细胞骨架重组， 粘附、迁移、存活和增殖。cdc 42有 被认为是通过生长因子介导Ras转化 受体并将细胞因子信号传递到细胞核中以影响细胞增殖。 在初步结果中，我们已经建立了一个基本的概念框架， Cdc 42靶向抑制白血病干细胞粘附和植入，促进LSC 从骨髓动员，并诱导LSC凋亡。我们有 还生成并建立了一系列重要的试剂、小鼠模型， 方法学，包括条件基因靶向小鼠模型，人 在“人源化”小鼠中的干/祖细胞转化的急性髓性白血病异种移植物模型， 前导Cdc 42活性特异性抑制剂卡辛，其能够特异性抑制 血液祖细胞中的Cdc 42活性和Cdc 42突变体重建/异种移植 在定义受调节的直接信号通路的要求时的加回方法 cdc42在这个提议中，我们将测试Cdc 42对细胞生长至关重要的假设。 维持BM生态位中的LSC，并代表了一种新的治疗靶点， 白血病根除我们将（1）在基因上验证Cdc 42作为小鼠AML的靶点 通过条件性基因靶向和突变体重建方法的发作和进展; (2)确定Cdc 42基因敲低对人类AML的影响和分子机制 在人源化小鼠模型中的进展;和（3）应用Cdc 42特异性抑制剂， 卡辛从异种移植小鼠骨中动员人AML白血病干细胞 骨髓，并检查卡辛与常规药物的组合效果 化疗药物对AML白血病干细胞根除的影响。我们的研究可能暗示 cdc 42作为细胞内信号流的关键节点，参与多种刺激， 白血病干细胞在骨髓小生境中的维持。结果将直接影响 在LSC中Cdc 42的药理学靶向治疗价值可能允许更多的 有效的联合化疗来根除白血病

Abstract The goals of this project are to use genetic means to demonstrate that the Rho GTPase, Cdc42 constitutes a novel target in leukemia stem cells (LSCs), and to apply a lead pharmacologic inhibitor of Cdc42 to suppress deregulated Cdc42 activity in human blood stem cell malignancies. The Cdc42 signaling axis lies at the crossroads of many signaling events and the functional interaction between Cdc42 and many of its implicated effectors mediate a variety of physiological responses including actin cytoskeletal reorganization, adhesion, migration, survival, and proliferation, of blood stem/progenitor cells. Cdc42 has been suggested to mediate Ras-transformation by signaling through growth factor receptors and to transduce cytokine signals into the nucleus to impact on cell proliferation. In the preliminary results, we have built up a basic conceptual framework suggesting that Cdc42 targeting can inhibit leukemia stem cell adhesion and engraftment, promote LSC mobilization from the bone marrow, and induce LSC apoptosis, in mouse models. We have also generated and established a collection of important reagents, mouse models, and methodologies including a conditional gene targeted mouse model, a human stem/progenitor transformed acute myeloid leukemia xenograft model in "humanized" mice, a lead Cdc42-activity specific inhibitor, CASIN, that is capable of specifically suppressing Cdc42 activity in blood progenitors, and Cdc42 mutant reconstitution/xenotransplantation add-back methods in defining the requirement of immediate signaling pathways regulated by Cdc42. In this proposal, we will test the hypothesis that Cdc42 is essential for the maintenance of LSCs in the BM niche and represents a novel therapeutic target for leukemia eradication. We will (1) genetically validate Cdc42 as a target in murine AML onset and progression by conditional gene targeting and mutant reconstitution approaches; (2) determine the effect and molecular mechanisms of Cdc42 knockdown on human AML progression in a humanized mouse model; and (3) apply the Cdc42-specific inhibitor, CASIN, to mobilization of human AML leukemia stem cells from xenograft mouse bone marrow and examine the combinatorial effect of CASIN together with the conventional chemotherapy agents on AML leukemia stem cell eradication. Our studies may implicate Cdc42 as a critical nodal of intracellular signal flows from multiple stimuli involved in leukemia stem cell maintenance in the bone marrow niche. The results will bear direct therapeutic value that pharmacologic targeting of Cdc42 in LSCs may allow for more effective combinatory chemotherapy in the effort to eradicate leukemia.