MECHANISM OF HOXA9 & MEIS1 PROTEIN INDUCED LEUKEMIA

HOXA9的机制

• 批准号: 6866813
• 负责人: COREY LARGMAN
• 金额: $ 33.41万
• 依托单位: NORTHERN CALIFORNIA INSTITUTE/RES/EDU
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-07-01 至 2009-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6866813
• 关键词: DNA binding protein; RNA interference; Retroviridae; acute myelogenous leukemia; cell transformation; gene deletion mutation; gene expression; genetic regulation; genetic regulatory element; genetic transcription; hematopoietic tissue; homeobox genes; laboratory mouse; leukemia; molecular oncology; mutant; neoplastic cell; neoplastic transformation; phosphorylation; protein localization; protein protein interaction; tissue /cell culture

DESCRIPTION (provided by applicant): HOXA9 expression is a common feature of human acute myelocytic leukemia (AML) and high level expression is correlated with poor prognosis. Moreover, HOXA9 overexpression immortalizes murine marrow progenitors which are arrested at a promyelocytic stage of differentiation when cultured, and causes leukemia in recipient mice following transplantation of HOXA9 expressing bone marrow. Our laboratory is now focused on developing treatment strategies based on blocking HOXA9 activity. Our recent data showed that protein kinase C (PKC) mediates phosphorylation of HOXA9 on S 204 and T205 at the N-terminus of the homeodomain. PKC phosphorylation of HOXA9 on S 204 abrogated the protein's DNA binding in vitro and the ability of endogenous HOXA9 to form cooperative DNA binding complexes with PBX. This HOXA9 phosphorylation was correlated with differentiation of myeloid cell lines and HOXA9-immortalized bone marrow cells. We hypothesize that this myeloid differentiation was in part due to PKC-mediated phosphorylation of HOXA9, which decreases the DNA binding of the homeoprotein. We have also recently determined the first set of downstream gene targets for HOXA9. We propose three aims: 1) to show a causal relationship between HOXA9 phosphorylation and myeloid differentiation, by elucidating the relationship between phosphorylation and HOXA9 pathological activity; 2) part I - determine which PKC isoform acts on HOXA9; part 2 - develop strategies to block HOXA9 transforming activity by: A) using RNAi to directly block HOXA9; B) using PKC stimulators or ser/thr phosphatase inhibitors to block HOXA9 activity in immortalized cell and leukemia models; and C) determine the X-ray crystal structure of HOXA9, to understand how phosphorylation blocks activity. This information will form the basis for future rationale drug design of HOXA9 inhibitors; and 3) to elucidate the direct molecular targets of the HOXA9 transcription factor with and without the MEIS1 and PBX cofactor proteins. The long range goal of this aim is to develop methods to block the biological activity of these downstream effector pathways. Taken together these studies should move us closer to achieving drug-based therapies for the treatment of acute myelogenous leukemias.

描述（申请人提供）：HOXA9表达是人类急性髓细胞白血病（AML）的共同特征，高水平表达与不良预后相关。 此外，HOXA9过度表达使小鼠骨髓祖细胞永生化，这些祖细胞在培养时被停滞在早幼粒细胞分化阶段，并在移植表达HOXA9的骨髓后在受体小鼠中引起白血病。 我们的实验室现在专注于开发基于阻断 HOXA9 活性的治疗策略。 我们最近的数据表明，蛋白激酶 C (PKC) 介导 HOXA9 在同源域 N 末端 S 204 和 T205 上的磷酸化。 HOXA9 在 S 204 上的 PKC 磷酸化消除了该蛋白的体外 DNA 结合以及内源性 HOXA9 与 PBX 形成协同 DNA 结合复合物的能力。 这种 HOXA9 磷酸化与骨髓细胞系和 HOXA9 永生化骨髓细胞的分化相关。 我们假设这种骨髓分化部分是由于 PKC 介导的 HOXA9 磷酸化，它减少了同源蛋白的 DNA 结合。 我们最近还确定了 HOXA9 的第一组下游基因靶标。我们提出三个目标：1）通过阐明磷酸化与HOXA9病理活性之间的关系，展示HOXA9磷酸化与骨髓分化之间的因果关系； 2) 第 I 部分——确定哪种 PKC 同工型作用于 HOXA9；第 2 部分 - 通过以下方式制定阻断 HOXA9 转化活性的策略： A) 使用 RNAi 直接阻断 HOXA9； B) 在永生化细胞和白血病模型中使用 PKC 刺激剂或丝氨酸/苏氨酸磷酸酶抑制剂来阻断 HOXA9 活性； C) 确定 HOXA9 的 X 射线晶体结构，以了解磷酸化如何阻断活性。 这些信息将构成 HOXA9 抑制剂未来药物设计的基础； 3) 阐明有或没有 MEIS1 和 PBX 辅因子蛋白的 HOXA9 转录因子的直接分子靶标。 该目标的长期目标是开发阻断这些下游效应途径的生物活性的方法。 总而言之，这些研究应该使我们更接近实现治疗急性髓性白血病的药物疗法。