The role of Rac and Rho GTPases in the development of myeloid leukemia

在急性髓系白血病(AML)中，恶性细胞与正常淋巴造血干细胞有很大的相似之处，包括自我更新的能力。正是这种转化的细胞群需要根除，才能实现持续缓解。近年来的研究表明，GTPase家族蛋白不仅在造血细胞的功能和发育中发挥重要作用，而且在髓系细胞的白血病转化过程中也起着重要作用。目前正在研究选择性地针对这些分子的新的RAC抑制剂。因此，我们建议评估小GTP酶在AML中作为潜在的额外靶分子的作用，以及它们与细胞遗传学改变的关系，以及它们在这种疾病中的预后价值。RhoH和RhoG的表达和Rac激活状态的影响将通过蛋白质印迹和Rac下拉实验以及利用siRNA或“基因k.o.”技术逆转录改变Rho基因的过表达或下调来研究。AML细胞的存活、凋亡、增殖和细胞周期控制将同时进行评估。体外研究将首先使用已建立的AML细胞系，然后再进行原代AML细胞。其他体内研究将在转基因小鼠白血病模型中进行，并通过将原代AML细胞异种移植到免疫缺陷小鼠中进行，这将进一步评估RAC抑制剂对疾病进展的影响。

In Acute myeloid leukemia (AML) the malignant cells retain considerable similarity to normal lymphohematopoetic stem cells including the ability to self-renewal. It is this transformed cell population that needs to be eradicated to achieve sustained remission. It has been demonstrated recently that GTPase family proteins not only play critical roles on function and development of hematopoetic cells but also contribute to leukemic transformation of myeloid cells. New Rac-inhibitors selectively targeting these molecules are currently under investigation. We therefore propose to assess the role of small GTPases as potential additional target molecules in AML and their association with cytogenetic alterations as well as their prognostic value in this disease. The effects of RhoH and RhoG expression and Rac activation status will be studied by western blot and Rac pull down experiments as well as retrovirally altered overexpression of Rho cDNA or Rho downregulation utilizing siRNA or “gene k.o.” – technology. AML cell survival, apoptosis, proliferation and cell cycle control will be evaluated in parallel. In vitro studies will initially use established AML cell lines before proceeding to primary AML cells. Additional in vivo studies will be performed in transgenic murine leukemia models and by xenotransplantation of primary AML cells into immunodeficient mice that will furthermore allow to evaluate the effect of Rac-inhibitors on disease progression.