Rac GTPases as targets in lymphomagenesis

摘要no - od -09-058: NIH宣布为竞争性修订申请提供恢复法案资金。该项目的目标是应用Rac gtpase与其调节鸟嘌呤核苷酸交换因子（GEFs）之间相互作用的机制见解，设计针对人类淋巴瘤中Rac活性失调的新型小分子抑制剂。GEF-Rac信号轴位于生长因子、细胞因子、应激和粘附分子引发的许多信号事件的十字路口。它们的功能相互作用导致Rac的激活和Rac介导的各种生理反应，包括肌动蛋白和微管细胞骨架重组、粘附、迁移和增殖。在父母资助中，我们试图确定Rac GTPase信号在p53缺陷小鼠和人类淋巴瘤模型中的作用，并暗示Rac信号作为一种有用的抗癌靶点。我们的跟踪记录和初步数据为研究Rac1与gef相互作用的结构-功能关系，获得涉及Rac1的几种功能相互作用的结构和动力学信息，以及通过条件基因靶向方法研究Rac1在小鼠中的作用提供了强有力的依据。特别是，我们发现了第一代小分子抑制剂NSC23766，它在体外和体内都能有效靶向Rac，并利用它研究了Rac gtpase从造血干细胞动员、血小板调节、神经鞘瘤表型逆转到淋巴瘤抑制等一系列生理和病理功能。在本补充提案中，我们将(1)基于新解析的Rac1-NSC23766晶体结构，通过虚拟筛选进行基于结构-功能的Rac靶向小分子抑制剂的合理设计和改进，(2)寻求通过药物化学改善Rac抑制剂的结构-活性关系，(3)在纯化的体外系统和细胞中验证新的Rac抑制剂。并将靶向Rac的小分子抑制剂应用于Rac活性异常高的p53缺陷淋巴瘤。这些基于机制的小分子抑制剂设计研究和新病理背景下的临床前验证将加快研究项目的速度，与父母资助资金协同作用，使创新和基于机制的基础科学假设更接近转化应用，并将在美国保留和创造就业机会。这些研究的终点将提供一代改进的Rac GTPase抑制剂，广泛用于癌症研究，特别是有效根除淋巴瘤。

DESCRIPTION (provided by applicant): Abstract NOT-OD-09-058: NIH Announces the Availability of Recovery Act Funds for Competitive Revision Applications. The goal of this project is to apply the mechanistic insights of the interaction between Rac GTPases and their regulatory guanine nucleotide exchange factors (GEFs), to the design of novel small molecule inhibitors targeting deregulated Rac activities in human lymphoma. The GEF-Rac signaling axis lies in the crossroads of many signaling events initiated by growth factors, cytokines, stress, and adhesion molecules. Their functional interaction leads to the activation of Rac and a variety of Rac-mediated physiological responses including actin and microtubule cytoskeletal reorganization, adhesion, migration, and proliferation. In the parental grant, we seek to define the role of Rac GTPase signaling in p53 deficient mouse and human lymphoma models and to implicate Rac signaling as a useful anti-cancer target. Our track record and preliminary data provide strong credential in studying the structure-function relationship of Rac1 in regard of its interaction with GEFs, in deriving structural and kinetic information of several functional interactions involving Rac1, and in studying the role of Rac1 by conditional gene targeting approach in mice. In particular, we have discovered a first generation small molecule inhibitor, NSC23766, that is effective in targeting Rac in vitro and in vivo, and have utilized it to study a number of physiological and pathological functions of Rac GTPases ranging from hematopoietic stem cell mobilization, platelet regulation, schwannoma phenotype reversion, to lymphoma suppression. In this supplemental proposal, we will (1) pursue structure-function based rational design and improvement of Rac-targeting small molecule inhibitors by virtual screening based on a newly resolved Rac1-NSC23766 crystal structure, (2) seek to improve the structure-activity relations of the Rac inhibitors by medicinal chemistry, and (3) validate the new Rac inhibitors in purified in vitro systems and in cells, and apply the Rac-targeting small molecule inhibitors to p53 deficient lymphoma where Rac activity is abnormally high. These mechanism-based studies of small molecule inhibitor design and pre- clinical validation in a novel pathologic context will accelerate the tempo of the research project to synergize with the parental grant funding to move an innovative and mechanism based, basic science hypothesis closer to translational applications, and will retain and create jobs in US. The end point of these studies will provide an improved generation of Rac GTPase inhibitors for a wide range of usage in cancer research, particularly for effective eradication of lymphoma. PUBLIC HEALTH RELEVANCE: Project Narrative The proposed work will pursue structure-based design of new chemical inhibitors of Rac GTPases by translating the mechanistic information obtained from the decade-long biochemical, structural, cell biological, and animal studies of Rac GTPases for anti-cancer therapy. Further, the proposed work will help establish a novel therapeutic concept that targeting Rac in p53 deficient lymphoma cells could be beneficial to conventional, chemoresistant cancer. The studies will accelerate the tempo of the research project to synergize with the parental grant funding to move an innovative and mechanism based, basic science hypothesis closer to translational applications, and will retain and create jobs in US.