Role of RNA Binding Proteins in BCR/ABL Leukemogenesis

描述（由申请人提供）：了解慢性粒细胞白血病（CML）疾病进展的生物学至关重要，因为疾病的晚期通常与令人沮丧的结局相关。我们广泛报道了mRNA代谢的改变是急变期CML（CML-BC）的一个关键特征。事实上，CML-BC中肿瘤抑制因子（例如PP 2A、C/EBPa）的功能丧失和原癌因子（例如MYC、MDM 2和BCL-XL）的表达增强是由异常的mRNA加工、核输出和/或翻译引起的。假定a）BCR/ABL水平在CML-BC白血病起始细胞中增加; B）BCR/ABL水平/活性与mRNA代谢改变之间存在因果关系;和c）对RNA结合蛋白hnRNPA 1、E2和K的表达和/或活性的分子和/或药理学干扰通过损害增殖拮抗体外和体内BCR/ABL白血病发生，抑制BCR/ABL+造血祖细胞的存活和/或恢复其分化;驱动这一提议的假设是BCR/ABL启动信号的分级激活，导致这些RNA结合蛋白的表达/功能在时间上和发育上有组织的增加，并且这代表疾病进展的必要步骤。基于这些考虑，总体目标是通过对BCR/ABL调节的hnRNP的表达/功能的时间变化及其与其他基因表达的转录后调节因子（例如microRNA）的相互作用/相互作用的综合体外和体内分析，进一步了解mRNA代谢改变对CML-BC病理生理学的重要性。具体而言，CML-BC标本、疾病进展的独特SCL-tTA-BCR/ABL小鼠模型和BCR/ABL+细胞系将用于评估1）hnRNP A1、K和E2表达/活性的BCR/ABL依赖性调节是否遵循分级顺序以及其发生在CML干细胞/祖细胞发育的哪个阶段; 2）hnRNP A1、E2和K表达/活性的体内调节防止CML母细胞转化;和3）miR-223和miR-328在CML-BC中的hnRNP E2增殖调节活性的调节中的体外和体内作用。如果成功的话，这项研究将正式建立CML进展，BCR/ABL表达和mRNA代谢改变之间的功能联系，并将表明能够拮抗BCR/ABL-hnRNP调节途径的药物在Ph 1白血病治疗中的结合，也许，其他癌症的特点是类似的mRNA代谢的改变。请注意，我们发现的BCR/ABL-hnRNP A1-SET-PP 2A抑制途径及其作为伊马替尼/达沙替尼敏感和耐药CML-BC和Ph 1 ALL的可行治疗靶点的重要性正在转化为临床试验。因此，拟议的研究与基础和转化癌症研究具有很强的相关性。公共卫生相关性：了解CML疾病进展的潜在机制至关重要，因为CML-BC通常对常规激酶抑制剂治疗无反应，并且通常与令人沮丧的结局相关。如果拟议的研究将确定RNA结合蛋白表达和功能的调节可以对抗疾病进展并有效诱导白血病起始细胞的细胞凋亡，那么可以在临床试验中评估能够改变异常hnRNP活性影响的药物的抗白血病作用。因此，很明显，如果成功，拟议的研究将对白血病研究和患者护理产生强烈影响。

DESCRIPTION (provided by applicant): Understanding the biology of Chronic Myelogenous Leukemia (CML) disease progression is of critical importance, as the advanced stage of the disease is often associated with a dismal outcome. We extensively reported that altered mRNA metabolism is a key feature of blast crisis CML (CML-BC). Indeed, loss-of-function of tumor suppressors (e.g. PP2A, C/EBPa) and enhanced expression of pro-oncogenic factors (e.g. MYC, MDM2 and BCL-XL) in CML-BC results from aberrant mRNA processing, nuclear export and/or translation. Given that a) BCR/ABL levels are increased in the CML-BC leukemia-initiating cell; b) a causal relationship exists between BCR/ABL levels/activity and altered mRNA metabolism; and c) molecular and/or pharmacologic interference with the expression and/or activity of the RNA binding proteins hnRNP A1, E2 and K antagonizes both in vitro and in vivo BCR/ABL leukemogenesis by impairing proliferation, inhibiting survival and/or restoring differentiation of BCR/ABL+ hematopoietic progenitors; the hypothesis driving this proposal is that BCR/ABL initiates a hierarchical activation of signals leading to a temporally- and developmentally-organized increase in the expression/function of these RNA binding proteins, and that this represents an essential step for disease progression. Based on these considerations, the overall objective is to further understand the importance of altered mRNA metabolism for the pathophysiology of CML-BC through an integrated in vitro and in vivo analysis of the temporal changes in expression/function of the BCR/ABL-regulated hnRNPs and of their interplay/interaction with other post-transcriptional regulators of gene expression (e.g. microRNAs). Specifically, CML-BC specimens, the unique SCL-tTA-BCR/ABL mouse model of disease progression and BCR/ABL+ cell lines will be used to assess whether 1) BCR/ABL-dependent regulation of hnRNP A1, K and E2 expression/activity follows a hierarchical order and at which stage of the CML stem/progenitor cell development it occurs; 2) in vivo modulation of hnRNP A1, E2 and K expression/activity prevents CML blastic transformation; and 3) in vitro and in vivo the role of miR-223 and miR-328 in the regulation of hnRNP E2 translation-modulatory activity in CML-BC. If successful, this investigation will formally establish a functional link between CML progression, BCR/ABL expression and altered mRNA metabolism, and will indicate the incorporation of drugs capable of antagonizing the BCR/ABL-hnRNP-regulated pathways in the therapy of Ph1 leukemias and, perhaps, of other cancers characterized by similar alteration in mRNA metabolism. Note that our discovery of the BCR/ABL-hnRNP A1-SET-PP2A inhibitory pathway and of its importance as a feasible therapeutic target in imatinib/dasatinib-sensitive and -resistant CML-BC and Ph1 ALL is in the process to be translated into clinical trials. Hence, the strong relevance of the proposed studies for basic and translational cancer research. PUBLIC HEALTH RELEVANCE: Understanding the mechanisms underlying CML disease progression is of critical importance, as CML-BC often does not respond to conventional kinase inhibitor therapy and is usually associated with a dismal outcome. If the proposed studies will determine modulation of RNA binding protein expression and function antagonize disease progression and efficiently induce apoptosis in the leukemia-initiating cells, the anti- leukemic effects of drug capable of altering the effects of aberrant hnRNP activity may be assessed in clinical trials. Thus, it is clear that, if successful, the proposed research will have a strong impact on leukemia research and patient care.