Targeting Cdc42 for bone marrow transplant therapies

 描述（由申请人提供）：动员的造血干细胞（HSC）移植已成为血液恶性肿瘤和血液疾病（例如白血病、骨髓衰竭综合征和多发性骨髓瘤）的护理标准。需要促进 HSC 植入的新方法来提高干细胞和基因疗法的功效和安全性，特别是对于那些传统 HSC 动员方案无效或清髓调理导致发病率和死亡率的患者。为此，开发更有效的 HSC 动员方法，并允许数量有限的 CD34 人类 HSC 或基因治疗校正的 HSC 增加植入和稳定嵌合，可能会对未来血液恶性肿瘤的干细胞移植实践产生重大影响。 Rho 家族 GTPase Cdc42 在调节细胞骨架动力学、ß1 整合素介导的粘附和 SDF-1a 诱导的定向迁移等方面发挥着关键作用，这些功能对于 HSC 驻留在骨髓生态位至关重要。在初步研究中，我们表征了条件基因靶向小鼠模型，并鉴定了 Cdc42 特异性小分子抑制剂，以定义 Cdc42 在 HSC 驻留骨髓中的作用。我们表明，Cdc42 的基因靶向或药理学靶向会导致功能性 HSC 的大量动员、骨髓生态位的短暂开放以及同基因或自体移植的 HSC 的有效植入。我们的结果表明，Cdc42 构成了参与骨髓 HSC 维持的细胞内信号流的关键节点，并导致我们的中心假设，即 Cdc42 对于 HSC 在 BM 生态位中的驻留至关重要，并且代表了 HSC 植入的有用靶点，这些特性有助于提高骨髓移植功效。拟议研究的目的是（1）确定先导 Cdc42 抑制剂的作用机制并通过药物化学提高先导疗效，以及（2）建立 Cdc42 靶向作为小鼠模型中 HSC 移植的非清髓性预处理方案的原理证明。通过实现这些早期药物发现研究的目标，我们可能会建立一种血液干细胞移植的新方法，这可能会对未来血液恶性肿瘤的细胞疗法产生重大影响。

 DESCRIPTION (provided by applicant): Transplantation of mobilized hematopoietic stem cells (HSCs) has become a standard of care for hematologic malignancies and blood diseases such as leukemia, bone marrow failure syndromes, and multiple myeloma. Novel methods promoting HSC engraftment are needed to improve the efficacy and safety of stem cell and gene therapies, especially for those patients where conventional HSC mobilization regimens are not effective or myeloablative conditioning leads to morbidity and mortality. To this end, developing more effective approaches for HSC mobilization and allowing increased engraftment and stable chimerism of quantity-limited CD34+ human HSCs or gene therapy-corrected HSCs could significantly impact on future stem cell transplantation practice for hematologic malignancies. The Rho family GTPase Cdc42 plays critical roles in regulating cytoskeleton dynamics, ß1 integrin-mediated adhesion, and SDF-1a induced directional migration, functions that are essential for HSC residence in the bone marrow niche. In preliminary studies we have characterized a conditional gene targeted mouse model and identified a Cdc42 specific small molecule inhibitor to define the role of Cdc42 in HSC residency in the bone marrow. We show that gene targeting or pharmacological targeting of Cdc42 causes massive mobilization of functional HSCs, transient opening of bone marrow niche, and effective engraftment of syngeneic or autolagous transplanted HSCs. Our results suggest that Cdc42 constitutes a critical nodal of intracellular signal flows involved in HSC maintenance in the bone marrow, and lead to our central hypothesis that Cdc42 is essential for HSC residence in the BM niche and represents a useful target for HSC engraftment, properties useful for improving bone marrow transplant efficacy. The aims of the proposed studies are (1) to define the mechanism of action of lead Cdc42 inhibitor and improve the lead efficacy by medicinal chemistry, and (2) to establish a proof of principle of Cdc42 targeting as a non- myeloablative conditioning regimen for HSC engraftment in mouse models. By achieving the goals of these early stage drug discovery studies, we may establish a new method for blood stem cell transplantation that may significantly impact on future cell therapies for blood malignancies.