Epigenetic regulation by microRNA of MDS pathogenesis

描述(申请人提供)：骨髓增生异常综合征(MDS)是一种无法治愈的干细胞疾病，通常进展为髓系白血病。一种异常的表观遗传调节在这种疾病的发病、进展和进化中起着至关重要的作用。到目前为止，MDS的有效治疗被证明是难以捉摸的，支持性护理用于改善症状，而造血干细胞移植是唯一可用的治疗选择。最近，通过抑制特定靶基因的表达，microRNAs被认为与血液系统恶性肿瘤有关。在此背景下，我们已经确定了一种致癌的microRNA，它增强了干细胞的自我更新，并重塑了血液系统恶性肿瘤的表观遗传学格局。为了通过TET2的活性更好地了解干细胞生物学和MDS发病机制中的关键途径，我们提出了以下具体目标：1.确定TET2如何直接参与致癌microRNA在造血中的功能我们已经产生了有条件地在造血室表达这种新发现的致癌microRNA的转基因小鼠，这反过来又表现出比对照细胞更低的10-11易位基因2(TET2)和全局5-羟甲基胞嘧啶的水平。生物信息学分析一直将TET2作为该microRNA的潜在靶点，其表达与我们MDS患者大型队列数据集中的TET2水平直接反相关，从而导致我们假设TET2是其关键靶点。目前的建议旨在阐明TET2的异位表达对该microRNA在体内和体外诱导的造血表型的影响。我们希望我们的研究将为靶向TET2治疗血液系统恶性肿瘤的治疗潜力提供理论基础。2.在MDS的临床前模型中测试microRNA抑制的治疗潜力。我们已经证明了这种微小RNA的异常表达与MDS低存活率之间存在直接的相关性。我们的初步研究结果表明，在体外，阻断这种microRNA降低了小鼠原代白血病细胞和人类白血病细胞系的致白血病活性，并伴随着TET2的升高，对正常小鼠造血的损害最小。为此，我们建议评估在人类原发白血病样本中抑制microRNA的安全性和有效性。我们将把这些发现与正在进行的骨髓增生异常综合征忠实小鼠模型的临床前试验数据结合起来，并最终探索启动正式临床试验以有效根除骨髓增生异常综合征的可能性。3.从机制上阐明microRNA-TET2途径调控的关键靶基因：为了进一步了解microRNA抑制TET2蛋白在造血过程中的后果，我们将检测microRNA-TET2信号通路异常对TET2蛋白可能靶点的影响。我们将重点分析这些基因在体内和体外对转基因小鼠的小鼠造血干细胞的遗传操作，以观察其在microRNA诱导的MDS发病中的后续作用。这些拟议的研究将不仅确定microRNA是一个强大的原癌基因，而且还将定义microRNA-TET2调节网络中的异常是血液系统恶性肿瘤中最常见的事件之一，具有重要的治疗意义。这项工作将在下列专家的支持下进行：David E.Avigan博士(血液学/肿瘤学)、Jan Vijg博士(遗传学、表观遗传学和microRNA生物发生学)、Julie Teruya-Feldstein博士(血液病理学)和Toshio suda博士(干细胞)。重要的是，Paul S.Frenette博士(干细胞利基)与Arthur Skoultchi博士(血液学表观遗传学重编程)密切支持我们的研究计划。

DESCRIPTION (provided by applicant): Myelodysplastic syndrome (MDS) is an incurable stem cell disorder that often progresses to myeloid leukemia. An abnormal epigenetic modulation has been highlighted as playing a crucial part in the pathogenesis, progress, and evolution of this disorder. To date, effective therapy for MDS has proved elusive, with supportive care used to ameliorate symptoms, and hematopoietic stem cell transplantation the only available curative option. MicroRNAs have recently been implicated in hematological malignancies through their inhibition of the expression of specific target genes. In this context, we have identified an oncogenic microRNA that enhances the self-renewal of stem cells and remodels the epigenetic landscape toward hematological malignancies. To better understand through its activity the key pathways involved in stem cell biology and MDS pathogenesis, we propose the following Specific Aims: 1. Determine how TET2 directly contributes to function of an oncogenic microRNA in hematopoiesis We have generated transgenic mice conditionally expressing this newly-identified oncogenic microRNA in the hematopoietic compartment, which in turn exhibits lower levels of ten-eleven translocation gene 2 (TET2) and global 5-hydroxymethylcytosine than control cells. Bioinformatics analyses have consistently identified TET2 as a potential target of this microRNA, whose expression was directly anti-correlated with the levels of TET2 in our large-cohort data set of patients with MDS, leading us to hypothesize that TET2 is its key target. The current proposal aims to elucidate the effect of ectopic expression of TET2 on the hematopoietic phenotypes induced by this microRNA both in vivo and in vitro. We expect our studies will provide a rationale for the therapeutic potential of targeting TET2 for the treatment of hematological malignancies. 2. Test the therapeutic potential of microRNA inhibition in preclinical models of MDS. We have shown a direct correlation between aberrant expression of this microRNA and poor MDS survival rates. Our preliminary findings demonstrated in vitro that blocking this microRNA reduces leukemogenicity in mouse primary leukemic cells and in human leukemia cell lines, accompanied by elevation of TET2, with minimal injury to normal murine hematopoiesis. In this aim, we propose to assess the safety and efficacy of inhibition of microRNA in human primary leukemia samples. We will integrate these findings with the data of ongoing pre-clinical trials in faithful mouse models of myelodysplastic syndrome, and will finally explore the potential to initiate formal clinical trial towards effective eradication of myelodysplastic syndrome. 3. To elucidate mechanistically the key target genes regulated by the microRNA-TET2 pathway: To further understand the consequences of repression of TET2 protein by the microRNA in hematopoiesis, we will examine the effects of aberrant microRNA-TET2 cross-talk on putative targets of TET2 protein. We will focus our analysis on the genetic manipulation of these genes, both in vivo and in vitro, in murine hematopoietic stem cells from transgenic mice, to observe the subsequent effects on MDS pathogenesis induced by microRNA. These proposed studies will not only identify microRNA as a potent proto-oncogene, but will also define aberrations in the microRNA-TET2 regulatory network as one of the most frequent events in hematological malignancies, with important therapeutic implications. This work will be conducted with the support of the following experts; Drs. David E. Avigan (Hematology/Oncology), Jan Vijg (Genetics, Epigenetics and microRNA biogenesis), Julie Teruya-Feldstein (Hemato-pathology), and Toshio Suda (Stem Cells). Importantly, Dr. Paul S. Frenette (Stem Cell niche) is closely supporting our research program along with Dr. Arthur Skoultchi (Epigenetic reprogramming in Hematology).