Project 2: Defining the role of megakaryocyte abnormalities in the progression of primary myelofibrosis

项目总结 纤维化前骨髓纤维化(PrePMF)于2016年由世界卫生组织正式确定 (世卫组织)作为一种新的早期惰性形式的MF，经常进展为骨髓纤维化(MF)，如 以及急性白血病。巨核细胞发育的异常调节是该病的关键特征 PrePMF和MF都是。在正常情况下，承诺的巨核祖细胞 在有限的范围内繁殖，然后产生少量的大型多倍体 分化的巨核细胞。然而，一旦获得了关键信号的突变 巨核系祖细胞的分子，如MPL、CALR或JAK2，扩大和促进 前PMF中的血小板增多和MF中的血小板减少/骨髓纤维化。之前的研究已经 证明了关键的巨核细胞转录因子GATA1的缺失导致了 小鼠骨髓中的GATA1水平显著降低 多发性骨髓瘤患者。我们假设在MF中GATA1的丢失导致了一个异常基因 表达计划，包括增加促纤维化和炎性细胞因子的水平 如转化生长因子-β、LNC2和IL-8，这些变化推动了从PMF前到MF的转变。 在我们的项目中，我们将首先对PrePMF和 动物模型和患者的MF巨核细胞，并确定这些变化是否会导致 巨核细胞异常生长和纤维化(目标1)。然后我们将评估具体的 转化生长因子-β对正常和骨髓间充质干细胞细胞周期的影响(目标2)。 最后，我们将使用目标1和目标2以及项目1和项目3中的信息来研究 靶向微环境、恶性造血干细胞或 动物模型中对MF的表观遗传调控。这项工作是创新的，因为没有人 描述了恶性巨核细胞引导PMF前期进展的方式， 相对良性阶段，相对于MF，这是MPNS造血失败的最后致命阶段。感谢 与该PPG的其他项目和核心的互动，我们处于独特的地位 明确巨核细胞影响前PMF向PMF转化的机制 转化生长因子-β、LCN2和IL-8在疾病中的作用我们的工作意义重大，因为它将有助于 项目4确定已在筹备中的MF临床试验的优先顺序，并导致新的靶向 MPN的治疗方法。

PROJECT SUMMARY Prefibrotic myelofibrosis (PrePMF) was formalized in 2016 by the World Health Organization (WHO) as a new early indolent form of MF which frequently progresses to myelofibrosis (MF) as well as acute leukemia. Abnormal regulation of megakaryocyte development is a key feature of both PrePMF and MF. Under normal conditions, committed megakaryocyte progenitors proliferate to a limited extent and then give rise to small numbers of large, polyploid differentiated megakaryocytes. However, upon acquisition of mutations in key signaling molecules, such as MPL, CALR or JAK2, megakaryocyte progenitors expand and promote thrombocytosis in PrePMF and thrombocytopenia/myelofibrosis in MF. Previous studies have demonstrated that a deficiency of the critical megakaryocyte transcription factor GATA1 leads a MF phenotype in mice and that levels of GATA1 are significantly reduced in the bone marrow of MF patients. We hypothesize that the loss of GATA1 in MF leads to an aberrant gene expression program which includes increased levels of pro-fibrotic and inflammatory cytokines such as TGF-β, LNC2 and IL-8, and that these changes drive the transition from Pre-PMF to MF. In our project, we will first perform a detailed assessment of cytokine secretion by PrePMF and MF megakaryocytes from animal models and patients and determine if these alterations induce aberrant megakaryocyte growth and fibrosis (Aim 1). Then we will assess the specific contributions of TGF-β to the cell cycle of normal and MF hematopoietic stem cells (Aim 2). Finally, we will use information from Aim 1 and 2, as well as from Projects 1 and 3, to study the efficacy of drugs that target the microenvironment, malignant hematopoietic stem cells or epigenetic regulators on MF in animal models. This work is innovative in that no one has characterized the way that malignant megakaryocytes guide the progression from Pre-PMF, a relative benign phase, to MF, the final fatal stage of hematopoietic failure in MPNs. Thanks to the interactions with the other projects and cores of this PPG, we are uniquely positioned to define the mechanisms by which megakaryocytes affect the transition from PrePMF to PMF and the contributions of TGF-β, LCN2 and IL8 to disease. Our work is significant in that it will assist Project 4 in prioritizing clinical trials already in the pipeline for MF and lead to new targeted therapies for the MPNs.