Targeting Cdc42 for bone marrow transplant therapies

 描述(申请人提供)：移植动员的造血干细胞(HSCs)已成为治疗恶性血液病和血液疾病(如白血病、骨髓衰竭综合征和多发性骨髓瘤)的标准疗法。为了提高干细胞和基因治疗的有效性和安全性，需要新的促进HSC植入的方法，特别是对于那些传统的HSC动员方案无效或清髓性预适应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，可能会对未来血液系统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、1整合素介导的黏附和SDF-1a诱导的定向迁移中起着关键作用，这些功能对于HSC在骨髓中的滞留是必不可少的。在初步研究中，我们已经确定了一个条件基因靶向的小鼠模型，并确定了一种CDC42特异性小分子抑制剂来确定CDC42在骨髓中HSC滞留中的作用。我们发现，基因打靶或药物打靶可以大量动员有功能的HSCs，瞬间打开骨髓穴，并有效地植入同种或自体移植的HSCs。我们的结果表明，CDC42是细胞内信号流的关键节点，参与了骨髓中HSC的维持，并导致了我们的中心假设，即CDC42对HSC在骨髓中的定位是必不可少的，并代表了HSC植入的有用靶点，这些特性有助于提高骨髓移植的效率。本研究的目的是(1)明确镉镉铅抑制剂的作用机制，并通过药物化学方法提高铅的疗效；(2)证明镉镉铅作为一种非清髓性的小鼠造血干细胞移植的预适应方案的原理。通过实现这些早期药物发现研究的目标，我们可能建立一种新的血液干细胞移植方法，这可能对未来血液恶性肿瘤的细胞治疗产生重大影响。

 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.