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有关。我们广泛报道，mRNA代谢异常是急变型CML(CML-BC)的一个重要特征。事实上，在CML-BC中，肿瘤抑制因子(如PP2A、C/EBPA)的功能丧失和癌前因子(如MYC、MDM2和bclxl)的表达增强是由于异常的mRNA加工、核输出和/或翻译造成的。鉴于a)在CML-BC白血病启动细胞中bcr/abl水平升高；b)bcr/abl水平/活性与改变的mRNA代谢之间存在因果关系；以及c)分子和/或药物干扰RNA结合蛋白hnRNP A1、E2和K的表达和/或活性，通过损害bcr/abl造血祖细胞的增殖、抑制存活和/或恢复分化来拮抗体外和体内bcr/abl白血病的发生；支持这一提议的假设是，BCR/ABL启动了信号的分级激活，导致这些RNA结合蛋白的表达/功能在时间和发育上的组织增加，这是疾病进展的关键步骤。基于这些考虑，总体目标是通过对BCR/ABL调节的hnRNPs的表达/功能的时间变化以及它们与其他转录后基因表达调控因子(如microRNAs)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。具体来说，将利用CML-BC标本、独特的SCL-TTA-BCR/ABL小鼠疾病进展模型和BCR/ABL细胞系来评估1)依赖BCR/ABL对hnRNP A1、K和E2表达/活性的调节是否遵循等级顺序以及它发生在CML干细胞/祖细胞发育的哪个阶段；2)在体内调控hnRNP A1、E2和K的表达/活性可防止CML母细胞转化；3)在体外和体内，miR-223和miR-328在CML-BC中对hnRNP E2翻译调节活性的调节作用。如果成功，这项研究将正式建立CML进展、bcr/abl表达和改变的mRNA代谢之间的功能联系，并将表明能够对抗bcr/abl-hnRNP调节的通路的药物被纳入PH1白血病的治疗中，可能还包括其他具有类似mRNA代谢改变特征的癌症的治疗。注意，我们发现了BCR/ABL-hnRNP A1-SET-PP2A抑制通路，并将其作为伊马替尼/达沙替尼敏感和耐药的CML-BC和PH1的可行治疗靶点的重要性，所有这些都正在转化为临床试验。因此，拟议的研究与基础和转化性癌症研究具有很强的相关性。与公共卫生相关：了解CML疾病进展的机制至关重要，因为CML-BC通常对传统的激酶抑制剂治疗没有反应，而且通常与令人沮丧的结果有关。如果所提出的研究将确定RNA结合蛋白的表达和功能的调节，以对抗疾病进展并有效地诱导白血病启动细胞的凋亡，则能够改变hnRNP活性异常的药物的抗白血病效果可能在临床试验中得到评估。因此，很明显，如果成功，拟议中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.