Role of SIRT7 in FLT3 ITD driven cell differentiation and transformation

受体酪氨酸激酶FLT3的致瘤性ITD突变是急性髓性白血病（AML）患者中重要的驱动突变之一。尽管midoin作为该癌基因的抑制剂被批准，FLT3 ITD阳性AML患者仍与预后不良相关。FLT3在促进髓细胞发育中的功能仍然不明确，尽管在AML中常见突变。定义分化途径是理解这种造血疾病发病机制的核心。我们的前期工作首次表明FLT3 itd为基础的髓系肿瘤的发展与SIRT7的表达作为控制HSC静止的因子的分子相关性。本项目申请的基础是我们关于SIRT7在髓系干细胞疾病中的作用的新发现，这些发现最近发表在白血病杂志上（Kaiser et al., 2020）。我们的工作证实SIRT7是年龄依赖性髓系干细胞疾病发展的重要因素，因此SIRT7表达的变化是FLT3 itd阳性AML细胞的相关病理机制。SIRT7水平低的AML患者预后较差，表明该蛋白与患者生存的临床相关性。SIRT7最近被发现是调节造血干细胞（HSC）静止和衰老的因子。造血系统内的分子改变影响细胞的寿命和分化。本项目的目的是剖析FLT3 ITD突变如何通过影响SIRT7的表达来诱导细胞分化，从而在体内驱动母细胞的骨髓扩增积累。通过使用原发性AML患者样本，建立体外模型细胞系统和小鼠模型，我们将研究SIRT7在FLT3 itd介导的骨髓异常和克隆扩增中的作用。在建立FLT3 -SIRT7信号与HSC分化/转化的分子相关性后，将设想HSC的再生策略（即SIRT7激活）。这可能在未来允许控制FLT3 ITD介导的HSC静止失衡，并随后抑制FLT3 ITD AML患者的骨髓分化。工作假设- SIRT7在AML （FLT3 ITD）细胞（细胞系，原代样品，小鼠BM细胞）中减少- FLT3 ITD激酶活性依赖性中SIRT7的抑制- c / ebp介导的SIRT7表达的控制受到FLT3 ITD的负调控- SIRT7的恢复诱导细胞分化并抑制细胞转化目的：1)表征FLT3 ITD对SIRT7活性的作用2)分析机制SIRT7如何在细胞水平上介导FLT3 ITD驱动的细胞转化/细胞分化iii)评估SIRT7在FLT3 ITD驱动的细胞转化/活体造血分化中的功能iv)通过激活细胞蛋白乙酰化影响FLT3 ITD介导的细胞转化

Oncogenic ITD mutations in the receptor tyrosine kinase FLT3 represent one of the important classes of driver mutations in Acute Myeloid Leukemia (AML) patients. Despite approval of Midostaurin as inhibitor of this oncogene, FLT3 ITD positive AML patients are still associated with poor prognosis. The function of FLT3 in promoting myeloid development remains poorly defined, despite being commonly mutated in AML. Defining differentiation pathways is central to understand pathogenesis of this hematopoietic disorder. Our preparatory work indicates for the first time a molecular correlation of FLT3 ITD-based development of myeloid neoplasms to the expression of SIRT7 as factor controlling HSC quiescence.The basis of this project application are our novel findings about the role of SIRT7 in myeloid stem-cell disorders, which were recently published in Leukemia (Kaiser et al., 2020). Our work established SIRT7 as important factor in the development of age-dependent myeloid stem-cell disorders and therefore changes of SIRT7 expression as a relevant pathomechanism in FLT3 ITD-positive AML cells. AML patients with low SIRT7 have poor prognosis demonstrating clinical relevance of this protein for patient survival. SIRT7 was recently identified as factor regulating hematopoietic stem cell (HSC) quiescence and aging. Molecular alterations within the hematopoietic system influence cellular longevity and differentiation. The aim of this proposed project is to dissect the mechanism, how FLT3 ITD mutations induce cell differentiation by affecting SIRT7 expression and thereby driving accumulation of myeloid expansion of blast cells in vivo. By using primary AML patient samples, established in vitro model cell systems and mouse models we will study the role of SIRT7 on FLT3 ITD-mediated myeloid aberrancies and clonal expansion. After establishing molecular correlation of FLT3 ITD-SIRT7-signalling on HSC differentiation/ transformation rejuvenation strategies of HSC (i. e. SIRT7 activation) will be envisaged. This could in the future allow to control FLT3 ITD-mediated imbalances of HSC quiescence and subsequently suppression of myeloid differentiation FLT3 ITD AML patients. Working hypotheses- SIRT7 is reduced in AML (FLT3 ITD) cells (cell lines, primary samples, mouse BM cells)- Suppression of SIRT7 in FLT3 ITD kinase activity dependent- C/EBP-mediated control of SIRT7 expression is negatively regulated by FLT3 ITD- Restoration of SIRT7 induces cell differentiation and suppresses cell transformationObjectivesi) Characterize the role of FLT3 ITD on SIRT7 activityii) Analyse the mechanism, how SIRT7 mediates FLT3 ITD-driven cell transformation/ cell differentiation on cellular leveliii) Assess function of SIRT7 on FLT3 ITD-driven cell transformation/ hematopoietic differentiation in vivoiv) Affecting FLT3 ITD mediated cell transformation by activation of the cellular protein acetylation