Targeting microRNAs to eradicate leukemia stem cells

白血病干细胞（LSC）包括急性或慢性白血病中的细胞亚群，其已经获得了造血干细胞。 “干细胞”的特性包括耐受无限自我更新的能力，维持异常克隆的能力， 并在暴露于化疗或其它生物应激物时达到静止，从而 从而对抗白血病治疗产生抗性。目前可用的细胞周期依赖性化疗和 其它分子靶向剂不能消除这些LSC。因此，新的有效治疗方法， 废除LSC是一个未满足的需求。microRNA（miRNAs）是一种短的非编码RNA，其调节细胞内的 多个靶蛋白，从而控制广泛的细胞程序。在那些 在白血病中下调，miR-126- 3 p（miR-126）的高表达与LSC基因表达相关 签名和糟糕的结果。此外，较高水平的miR-126控制正常人和正常人的静止， miR-126活性降低可增加造血干细胞（HSC）和LSC的造血干细胞（LSC）的增殖，但当miR-126活性减弱时， 输出，它会使LSC耗尽。该提议的中心假设是miR-126对于细胞的增殖和分化至关重要。 LSC的体内平衡和介导LSC治疗抗性，因此代表了一种有前途的LSC导向的 治疗靶点本申请的主要目的是了解miR-126的表达是如何在细胞内表达的。 在LSC中异常调节，并开发有效的治疗方法来抑制LSC中的miR-126， 从而避免正常的造血。作为原理证明，我们将专注于在急性髓系白血病中靶向miR-126。 (AML)和慢性粒细胞白血病（CML），但类似的原则可以扩展到其他类型的白血病。 白血病我们提出了以下具体目标（SA）：SA 1。为了剖析并克服 新发现的SPRED 1/miR-126自身调节因子介导的治疗耐药机制 在LSC中循环。我们将测试酪氨酸激酶（TK）依赖性SPRED 1/miR-126自动调节环是否与细胞增殖有关。 在AML和CML中有效，其介导miR-126依赖性酪氨酸激酶耐药机制 抑制剂（TKI）。我们将1）评估SPRED 1/miR-126自动调节环在不同亚型的乳腺癌中的活性， AML; 2）确定TK依赖性SPRED 1磷酸化位点; 3）创建白血病小鼠模型以解剖AML细胞; SPRED 1/miR-126自动调节环与异常活性TK相互作用。SA 2.为了确定miR的作用， 126在维持骨髓微环境内的LSC小生境中的作用。我们将从基因上 在LSC和内皮细胞（EC）中具有条件性miR-126缺失的工程化AML和CML模型。我们将 确定1）由LSC产生的miR-126的贡献; 2）miR-126在EC中的贡献 3）miR-126的缺失是否可以增强治疗介导的LSC消除。SA 3.到 开发和优化靶向LSC和LSC小生境中miR-126的合成抑制剂。我们将 进行PK和PD分析和临床前研究，以确定antimiR-126的活性剂量/时间表 与CpG-寡脱氧核苷酸（ODN）偶联，用于最佳靶向细胞递送。

Leukemia stem cells (LSC) comprise subpopulations of cells in acute or chronic leukemia that have acquired “stem cell” properties including the ability to endure unlimited self-renewal, maintain aberrant clonal hematopoiesis and achieve quiescence upon exposure to chemotherapy or other bio-stressors thereby conferring resistance to antileukemia treatments. Currently available cell-cycle-dependent chemotherapy and other molecular targeting agents are unable to eliminate these LSCs. Thus new effective treatments to abrogate LSC are an unmet need. MicroRNAs (miRNAs) are short non-coding RNAs that regulate levels of multiple target proteins, thereby controlling a wide array of cellular programs. Among miRNAs that are deregulated in leukemia, higher expression of miR-126-3p (miR-126) is associated with LSC-gene expression signatures and poor outcome. Furthermore, higher levels of miR-126 controls quiescence both in normal hematopoietic stem cells (HSC) and LSC, but while attenuated miR-126 activity increases HSC hematopoietic output, it drives LSC to exhaustion. The central hypothesis of this proposal is that miR-126 is critical for the homeostasis of LSC and mediates LSC therapy resistance, thus represents a promising LSC-directed therapeutic target. The major objective of this application is to understand how miR-126 expression is aberrantly regulated in LSC and to develop an effective therapeutic approach to inhibit miR-126 in LSC, while sparing normal hematopoiesis. As a proof-of-principle, we will focus on targeting miR-126 in acute myeloid (AML) and chronic myeloid leukemia (CML), but similar principles could be expanded to other types of leukemia. We propose the following specific aims (SA): SA1. To dissect and overcome the molecular mechanisms of therapy resistance mediated by a newly discovered SPRED1/miR-126 autoregulatory loop in LSC. We will test that a tyrosine kinase (TK)-dependent SPRED1/miR-126 autoregulatory loop is operative in AML and CML, which mediate miR-126-dependent mechanisms of resistance to tyrosine kinase inhibitors (TKI). We will 1) assess the activity of SPRED1/miR-126 autoregulatory loop in distinct subtypes of AML; 2) define TK-dependent SPRED1 phosphorylation sites; 3) create leukemia mouse models to dissect the interplay of SPRED1/miR-126 autoregulatory loop with aberrantly active TK. SA2. To define the role of miR- 126 in maintaining a LSC niche within the bone marrow microenvironment. We will develop genetically engineered AML and CML models with conditional miR-126 deletion in LSC and endothelial cells (EC). We will determine 1) the contribution of miR-126 produced by LSC; 2) the contribution of miR-126 in the EC compartment; 3) whether deletion of miR-126 could enhance treatment-mediated elimination of LSC. SA3. To develop and optimize a synthetic inhibitor that targets miR-126 in LSC and the LSC niche. We will perform PK and PD analyses and preclinical studies to define the active dose/schedule of an antimiR-126 conjugated with CpG-oligodeoxynucleotide (ODN) for optimal targeted cell delivery.