Dissection of Molecular Pathways Downstream of HOXA9 & Discovery of New Drug Trgt

在小鼠和人类中的研究表明，主要HOX基因可能整合骨髓增生异常和白血病的活动， 高危人类骨髓增生异常综合征（MDS）中几种不同的致癌蛋白和分子途径， 促进其进展为急性髓性白血病（AML）。本提案中总结的研究表明， 在多能骨髓干细胞中HOXA 9释放a转化途径的上调，最初导致 三系发育不良和染色体不稳定性，最终导致具有复杂核型的高危AML， 无论治疗效果如何，结果都很差。尚不可能描绘HOXA 9下游的分子途径， 阻碍了鉴定可能成为小分子抑制剂设计的特异性靶点的关键蛋白质的努力， 治疗MDS和预防进展为AML。像HOXA 9这样的转录因子还没有被证明是 小分子抑制的靶点，因此描绘关键的下游途径对于设计 靶向治疗。本项目开发的新机会是小抑制RNA（siRNA） 在人类AML细胞系中"敲低" HOXA 9水平的策略，因此下调HOXA 9水平的细胞生物学后果， 关键的HOXA 9介导的途径可以被定义。初步数据证明我们有能力"击倒" HOXA 9水平 低于人类AML细胞系中预先存在水平的10%。我们还发现HOXA 9的下调显著地 延缓这些细胞的生长，表明HOXA 9在维持改变的干细胞的增殖能力中的作用 在额外的遗传物质积累后， 异常我们的基本假设是，我们将确定HOXA 9内的下游靶点， 导致MDS中造血细胞发育紊乱和白血病转化为 AML，包括作为酶起作用并且可以被小分子有利地抑制的那些。的 这些靶标的鉴定将通过使用微阵列的基因表达分析和 染色质免疫沉淀技术。HOXA 9靶点的重要性将通过"敲低"验证 以及评估功能抑制是否也延缓骨髓细胞中的异常细胞生长 线模型系统。阳性结果将提供这样的蛋白质是可用的靶点的原理证明。 药物或小分子抑制剂的开发，可以在项目1中快速测试。

Studies in mice and humans suggest major HOX genes may integrate myelodysplastic and leukemogenic activities of several different oncogenic proteins and molecular pathways in high risk human myelodysplastic syndrome (MDS) and promote its progression to acute myeloid leukemia {AML). Studies summarized in this proposal suggest that upregulation of HOXA9 elicits a transforming pathway in pluripotent bone marrow stem cells, leading initially to trilineage dysplasia and chromosomal instability and culminating in high risk AML with complex karyotypes and very poor outcomes regardless of therapy. It has not been possible to delineate molecular pathways downstream of HOXA9, impeding efforts to identify key proteins that could be specific targets for the design of small molecule inhibitors for treatment of MDS and prevention of progression to AML. Transcription factors like HOXA9 have not been proven to be targets for inhibition by small molecules, so delineation of crucial downstream pathways is critical for the design of targeted therapies. The new opportunity to be exploited in this project is development of small inhibitory RNA (siRNA) strategies to "knock-down" HOXA9 levels in human AML cell lines, so cell biologic consequences of down-regulating crucial HOXA9-mediated pathways can be defined. Preliminary data attest to our ability to "knock-down" HOXA9 levels to less than 10% of preexisting levels in human AML cell lines. We also show that down-regulation of HOXA9 markedly retards growth of these cells, suggesting an effect of HOXA9 in maintaining proliferative capacity of altered stem cells that give rise to MDS and eventually contribute to leukemic transformation, after accumulation of additional genetic abnormalities. Our fundamental hypothesis is that we will identify downstream targets within the HOXA9 pathway that contribute to disordered hematopoietic cell development in MDS and leukemic transformation to AML, including those that function as enzymes and can be advantageously inhibited by small molecules. The identification of these targets will be addressed by a combination of gene expression analysis using microarrays and chromatin immunoprecipitation techniques. The significance of HOXA9 targets will be validated by "knocking-down" protein levels with siRNA and assessing whether function inhibition also retards aberrant cell growth in a myeloid cell line model system. A positive result would provide proof-of-principle that such proteins are suitable targets for available drugs or the development of small molecule inhibitors that could be rapidly tested in Project 1.