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，通常进展为骨髓性白血病。一个异常的表观遗传调制已被强调为在这种疾病的发病机制，进展和演变中发挥着至关重要的作用。迄今为止，MDS的有效治疗已被证明是难以捉摸的，支持性护理用于改善症状，造血干细胞移植是唯一可用的治疗选择。最近发现microRNA通过抑制特定靶基因的表达而与血液恶性肿瘤有关。在这种情况下，我们已经确定了一种致癌的microRNA，它可以增强干细胞的自我更新，并重塑血液恶性肿瘤的表观遗传景观。为了通过其活性更好地了解干细胞生物学和MDS发病机制中涉及的关键途径，我们提出了以下具体目的：1.确定TET 2如何直接促进造血中致癌microRNA的功能我们已经产生了在造血区室中条件性表达这种新鉴定的致癌microRNA的转基因小鼠，其反过来表现出比对照细胞更低水平的10 - 11易位基因2（TET 2）和全局5-羟甲基胞嘧啶。生物信息学分析一直将TET 2确定为这种microRNA的潜在靶标，其表达与我们的MDS患者大队列数据集中的TET 2水平直接反相关，这使我们假设TET 2是其关键靶标。目前的建议旨在阐明TET 2的异位表达对这种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TET 2治疗血液恶性肿瘤的治疗潜力提供理论依据。2.在MDS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microRNA的异常表达与MDS生存率低下之间的直接相关性。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白血病细胞系中的白血病发生，伴随着TET 2的升高，对正常小鼠造血的损伤最小。在这个目标中，我们建议评估在人类原发性白血病样本中抑制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相结合，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.为了从机制上阐明microRNA-TET 2途径调控的关键靶基因：为了进一步了解造血中microRNA对TET 2蛋白的抑制作用，我们将研究异常microRNA-TET 2串扰对TET 2蛋白推定靶点的影响。我们将集中我们的分析，这些基因的遗传操作，在体内和体外，在小鼠造血干细胞从转基因小鼠，观察随后的影响MDS的发病机制所诱导的microRNA。这些拟议的研究不仅将microRNA确定为一种有效的原癌基因，而且还将microRNA-TET 2调控网络中的畸变定义为血液恶性肿瘤中最常见的事件之一，具有重要的治疗意义。这项工作将在以下专家的支持下进行：大卫E。Avigan（血液学/肿瘤学）、Jan Vijg（遗传学、表观遗传学和microRNA生物发生）、Julie Teruya-Feldstein（血液病理学）和Toshio苏达（干细胞）。重要的是，保罗·S。Frenette（干细胞利基）与亚瑟斯库尔奇博士（血液学中的表观遗传重编程）一起沿着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).