Role of microRNAs in the regulation of CML stem cell self renewal and survival

描述(申请人提供)：慢性粒细胞白血病(CML)是第一种临床治愈的干细胞来源的造血肿瘤；然而，酪氨酸激酶抑制剂(TKI)治疗会留下一批对这些药物表现出天生耐药性的细胞池。这些是静止的慢性粒细胞白血病干细胞(HSC)，代表着活跃的癌症储备库。因此，很明显，只有能够安全有效地针对这些HSCs而不损害正常HSCs的药物才有可能导致疾病根除。我们已发表的和初步的数据表明，一种可能的机制涉及激酶(即BCR-ABL1和JAK2)和磷酸酶(即PP2A)之间的异常平衡，这可能取决于特定microRNAs(MiRs)的表达变化。事实上，我们发现miRs的表达发生了变化，可能针对JAK2-hnRNP A1-Set/PP2A-吗-catenin HSC途径，这对静止的CML HSC的生存和自我更新是必不可少的，但以BCR-ABL1表达的方式运作--而不是依赖于激酶。鉴于a)BCR-ABL1蛋白而不是mRNA和JAK2的表达/活性在静止的CML HSCs中升高；b)miR水平在白血病中异常表达，并且干/祖细胞发生变化；以及c)最近发现的RNA诱骗活性不仅限于miR-328，而且其他miR可能与hnRNP功能相互作用和干扰；支持这一提议的假设是，静止的Ph HSCs显示出调控失调的miR表达，该表达依赖于BCR-ABL1的表达，而不是激酶活性，并且有助于增强白血病HSC的存活和自我更新。基于这些考虑，本建议的总体目标是了解miR表达变化对维持CML HSCs静止库的需求，并通过鉴定和整合体外和体内分析miR的表达来确定药物恢复miR表达的治疗意义，miR以规范的和/或诱骗的方式通过直接干扰BCR-ABL1-JAK2-hnRNP A1-SET-ç-catenin途径影响CML HSC的存活和自我更新。因此，为了实现这些目标，我们将依靠来自CML患者的高度富含HSC的CD34/CD38-(CD90)BM细胞、独特的SCL-TTA-BCR/ABL小鼠模型和合成的miR或antagomiR来治疗移植了GFP/Luc CML HSCs的NSG小鼠，以：1)识别CML HSC中通过其规范和/或hnRNP A1诱骗活性干扰BCR-ABL1-JAK2途径的miR；2)评估miR水平的调节是否损害CML HSCs的存活和自我更新；3)用2-O-MEPs、miR和抗核抗体确定miR表达调控在CML根治中的治疗作用。我们相信，拟议工作的成功完成将促进我们对白血病HSC生物学的了解，根据我们在过去几年中的发现，可以肯定地预测，这一领域将出现新的观察结果，其中一些将揭示治疗干预的新策略。因此，这项工作对于基础和转化性癌症研究具有很强的重要性和高度相关性。

DESCRIPTION (provided by applicant): Chronic myeloid leukemia (CML) is the first "clinically cured" stem cell-derived hematopoietic neoplasm; however, tyrosine kinase inhibitor (TKI) therapy leaves behind a pool of cells showing innate resistance to these drugs. These are quiescent CML stem cells (HSC) that represent an active cancer reservoir. Thus, it becomes clear that only drugs that can safely and efficiently target these HSCs without harming the normal ones have the potential to lead to disease eradication. Our published and preliminary data suggest that a likely mechanism involve an aberrant balance between kinases (i.e. BCR-ABL1 and Jak2) and phosphatases (i.e. PP2A) and this may depend on altered expression of specific microRNAs (miRs). In fact, we found altered expression of miRs that may target the Jak2-hnRNP A1-SET/PP2A-ß-catenin HSC pathway, which is essential for survival and self-renewal of quiescent CML HSCs but operates in a BCR-ABL1 expression- but not kinase- dependent manner. Given that a) BCR-ABL1 protein but not mRNA and Jak2 expression/activity are elevated in quiescent CML HSCs; b) miR levels are aberrant in leukemias and change in stem vs. progenitor cells; and c) the recently discovered RNA decoy activity is not limited to miR-328 but other miRs likely interact and interfere with hnRNP function; the hypothesis driving this proposal is that quiescent Ph+ HSCs display a dysregulated miR expression which depends on BCR-ABL1 expression but not kinase activity, and contributes to enhanced survival and self-renewal of leukemic HSCs. Based on these considerations, the overall objective of this proposal is to understand the requirement of altered miR expression for the maintenance of the quiescent reservoir of CML HSCs and determine the therapeutic relevance of pharmacologic restoration of miR expression through the identification and integrated in vitro and in vivo analysis of the miRs, which in a canonical and/or decoy manner, affect CML HSC survival and self-renewal through direct interference with the BCR-ABL1-Jak2-hnRNP A1-SET-ß-catenin pathway. Thus, to accomplish these goals we will rely on the use of highly HSC-enriched CD34+/CD38-(CD90+) BM cells form CML patients, the unique SCL-tTA-BCR/ABL mouse model and synthetic miRs or antagomiR to treat NSG mice transplanted with GFP+/Luc+ CML HSCs in order to: 1) Identify miRs dysregulated in CML HSCs that interfere with the BCR-ABL1-Jak2 pathway through their canonical and/or hnRNP A1 decoy activities; 2) Assess whether modulation of miR levels impairs in vitro and in vivo survival and self-renewal of CML HSCs; and 3) Determine the therapeutic role of modulation of miR expression in eradication of CML by using 2-O-MePS miRs and antagomiRs. We are confident that the successful completion of the proposed work will advance our knowledge of leukemic HSC biology and, based on the discoveries we made in the past few years, it is safe to predict that new observations will be made in this field and that some of them will reveal new strategies for therapeutic intervention. Hence, the strong importance and high relevance of this work for basic and translational cancer research.