Human Hematopoietic Cell Transformation by BCR/ABL

描述(申请人提供)：慢性粒细胞白血病(CML)由bcr/abl癌基因转化为非常原始的造血细胞，其特征是骨髓增殖增加和恶性前体细胞的异常运输。CML祖细胞在造血调控方面表现出几种异常，包括生长因子诱导的增殖增加，与纤维连接蛋白的黏附减少，对SDF-1a的趋化减少。尽管酪氨酸激酶抑制剂甲磺酸伊马替尼在治疗慢性粒细胞白血病方面非常有效，但对恶性前体细胞的消除往往是不完全的，可能会出现临床耐药。因此，针对BCR/ABL激活的信号机制的其他治疗方法对转化具有重要意义。不同的bcr/abl机制对转化的贡献因细胞类型不同而不同，已知的机制对人类造血细胞转化的贡献尚不清楚。这项拟议研究的目标是研究对人类祖细胞转化至关重要的分子机制。在初步研究中，我们研究了CML患者CD34祖细胞细胞内信号的异常。我们还开发了一种新的CML模型，该模型基于BCR/ABL基因在人CD34细胞中的异位表达，复制了原始CML祖细胞的造血调节异常，有助于研究CML转化的分子机制。初步研究发现，BCR/ABL蛋白结构域可能与异常的祖细胞生长和黏附密切相关。在特定的目标1中，我们将研究bcr Y177上的一个自动磷酸化位点及其下游信号通过Grb2、Gab2和Shp2在表达bcr/abl的人祖细胞异常增殖和凋亡中的作用。在特定的目标2中，我们将研究BCR/ABL转化的人祖细胞异常黏附和趋化的机制。最后，在特定的目标3中，我们将研究抑制上述信号通路是否可以在与伊马替尼联合使用时加强对CML祖细胞生长的抑制，和/或是否可以由于激酶域的突变而抑制对伊马替尼耐药的祖细胞的生长。这些研究有望提高对慢性粒细胞白血病中人类祖细胞转化的关键机制的理解，并指导合理开发其他基于机制的治疗方法。

DESCRIPTION (provided by applicant): Chronic myelogenous leukemia (CML) results from the transformation of a very primitive hematopoietic cell by the BCR/ABL oncogene and is characterized by increased myeloproliferation and abnormal trafficking of malignant progenitors. CML progenitors demonstrate several abnormalities in hematopoietic regulation including increased growth factor-induced proliferation, reduced adhesion to fibronectin and reduced chemotaxis towards SDF-1a. Although the tyrosine kinase inhibitor imatinib mesylate is very effective in the treatment of CML, elimination of malignant progenitors is often incomplete and clinical resistance can occur. Therefore, additional treatment approaches to target BCR/ABL activated signaling mechanisms important for transformation are of high priority. The contribution of different BCR/ABL mechanisms to transformation varies from 1 cell type to the other, and the contribution of known mechanisms to human hematopoietic cell transformation is not clear. The goal of the proposed studies is to investigate molecular mechanisms that are critical for human progenitor transformation. In preliminary studies, we have investigated abnormalities in intracellular signaling in CD34+ progenitor cells from CML patients. We have also developed a novel CML model based on ectopic expression of the BCR/ABL gene in human CD34+ cells, which reproduces abnormalities in hematopoietic regulation seen in primary CML progenitors and facilitates study of molecular mechanisms of transformation. Preliminary studies have identified BCR/ABL protein domains that may significantly contribute to abnormal progenitor growth and adhesion. In Specific Aim 1 we will investigate the role of an autophosphorylation site at BCR Y177 and downstream signaling through Grb2, Gab2 and Shp2 in abnormal proliferation and apoptosis of BCR/ABL expressing human progenitors. In Specific Aim 2 we will investigate the mechanisms of abnormal adhesion and chemotaxis in BCR/ABL transformed human progenitors. Finally, in Specific Aim 3 we will investigate whether inhibition of the above signaling pathways can enhance suppression of CML progenitors growth when combined with imatinib, and/or can suppress growth of progenitors resistant to imatinib because of kinase domain mutations. These studies are expected to result in improved understanding of mechanisms critical for human progenitor transformation in CML and guide rational development of additional mechanism-based therapies.