Triad1 regulates myelopoiesis and functions as a leukemia suppressor

Triad1 调节骨髓细胞生成并发挥白血病抑制因子的作用

• 批准号: 9032480
• 负责人: Elizabeth Ann Eklund
• 金额: $ 35.34万
• 依托单位: NORTHWESTERN UNIVERSITY AT CHICAGO
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2020-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9032480
• 关键词: 11q23; Acute Myelocytic Leukemia; Affinity; Apoptosis; Bone Marrow; CREBBP gene; Cell Proliferation; Cell Survival; Cells; Chimeric Proteins; Cytokine Receptors; Development; Disease Progression; Drug resistance; EGF gene; Epithelial Cells; Event; FLT3 gene; Feedback; Gene Targeting; Genes; Genetic Transcription; Goals; Granulopoiesis; Growth; Health; Homeobox Genes; Human; Hypersensitivity; In Vitro; Incidence; Individual; Inositol; Integrin alphaV; Integrin alphaVbeta3; Integrin beta3; Integrins; Lesion; MLL gene; Mediating; Modeling; Molecular; Mus; Mutation; Myelogenous; Myeloid Cells; Myelopoiesis; Myeloproliferative disease; Phosphorylation; Phosphotransferases; Production; Proteins; Recycling; Refractory; Repression; Role; Sampling; Signal Transduction; Stem cells; Stream; TP53 gene; Time; Transplantation; Tyrosine Phosphorylation; Ubiquitin; Ubiquitination; autocrine; cytokine; homeodomain; in vivo; leukemia; leukemogenesis; mouse model; mutant; novel; outcome forecast; overexpression; prevent; progenitor; promoter; receptor; response; therapeutic target; transcription factor; ubiquitin-protein ligase

 DESCRIPTION (provided by applicant): Triad1 is an E3 ubiquitin ligase that impairs proliferation of bone marrow progenitor cells and increases in expression during granulopoiesis. We found that Triad1 enhances ubiquitin (Ub) mediated degradation of Fgf- R1, Flt3 and av integrin in myeloid cells. Fgf-R1 and Flt3 activate phospho-inositol-3-kinase; resulting in stabilization of ßcatenin and expression of ßcatenin-target-genes involved in proliferation/survival. Syk is activated by avß3 integrin, resulting in Pak1-dependent proliferatin and PLC-dependent survival. Triad1 also inhibits Ub of p53 by Mdm2. We hypothesize that increasing Triad1 expression during granulopoiesis favors degradation of Fgf-R1, Flt3 and avß3 integrin, but stabilizes p53; decreasing proliferation and enhancing sensitivity to apoptosis. This identifies a possible leukemia suppressor function for Triad1, since impaired activity would sustain Fgf-R1, Flt3 and avß3 signaling and destabilize p53. Consistent with this, Triad1 is specifically decreased in subsets of acute myeloid leukemia (AML) with MLL-translocations (i.e. 11q23-AML) or activating FLT3 mutation. Our studies identified a mechanism for this. 11q23-AML is characterized by increased expression of a set of HOX genes, including HoxA9 and A10. We found that HoxA9 and A10 regulate transcription of ARIH2 (encoding Triad1) in a manner that requires cytokine-induced tyrosine phosphorylation of the Hox proteins. We found that constitutive activation of Shp2-PTP blocks ARIH2 transcription by preventing Hox phosphorylation. Interestingly, FLT3 mutations are frequent in Hox-over- expressing AML and activate Shp2. A myeloproliferative neoplasm (MPN) develops in mice transplanted with bone marrow expressing MLL1 fusion proteins or overexpressing HoxA9 or A10. This MPN evolves to AML over time, suggesting that Hox-overexpression is inadequate for AML in the absence of cooperating mutations. We find constitutive Shp2-activation performs this function. We hypothesize Triad1 is a leukemia suppressor that decreases proliferation/survival of cytokine-stimulated progenitor cells, and that impaired Triad1-activity facilitates disease progression/drug resistance in Hox-overexpressing AML. We will pursue this via 3 aims: Aim 1: Identify Triad1-regulated events that have functional implications for leukemia. The influence of Triad1 on Ub/degradation of Fgf-R1, avß3, Flt3 and p53 will be investigated in vitro and in vivo. Aim 2: Determine if Triad1 is a leukemia suppressor in AML with Hox-overexpression and Shp2 activation. The contributions of Triad1-expression and Shp2-activation to drug resistance/disease progression will be explored in studies with murine AML models and human AML bone marrow samples. Aim 3: Define targetable mechanisms of leukemia suppression by Triad1. Contributions of Fgf-R1, Flt3, av integrin and p53 to leukemogenesis and drug resistance will be explored in vivo in murine models. Hox-overexpressing AML has poor prognosis and is treatment refractory. Clarifying cooperating lesions and down-stream events may suggest therapeutic targets for this subset of individuals.

 描述(申请人提供)：Triad1是一种E3泛素连接酶，可损害骨髓祖细胞的增殖并在粒细胞生成过程中增加表达。我们发现Triad1可促进泛素(Ub)介导的髓系细胞对成纤维细胞生长因子-R1、Flt3和av整合素的降解。成纤维细胞生长因子-R1和Flt3激活了磷酸肌醇-3-激酶，从而稳定了？连环蛋白，并稳定了与增殖/存活相关的？连环蛋白靶基因的表达。SYK被av？3整合素激活，导致Pak1依赖的增殖素和PLC依赖的生存。Triad1还通过MDM2抑制P53的Ub。我们假设，在粒细胞生成过程中，增加Triad1的表达有利于FGF-R1、Flt3和av？3整合素的降解，但稳定P53；抑制增殖并增强对凋亡的敏感性。这 确定了Triad1可能的白血病抑制功能，因为活性受损将维持FGF-R1、Flt3和av？3信号转导，并破坏p53的稳定。与此一致，Triad1在有MLL易位(即11q23-AML)或激活Flt3突变的急性髓系白血病(AML)亚群中特异性降低。我们的研究确定了这一现象的机制。11q23-AML的特征是一组HOX基因表达增加，包括HoxA9和A10。我们发现，HoxA9和A10调节Arih2(编码Triad1)的转录，这种方式需要细胞因子诱导Hox蛋白的酪氨酸磷酸化。我们发现Shp2-PTP的结构性激活通过阻止Hox的磷酸化来阻止Arih2的转录。有趣的是，在Hox过度表达的AML中，Flt3突变频繁，并激活Shp2。骨髓增生性肿瘤(MPN)发生在骨髓移植表达MLL1融合蛋白或过表达HoxA9或A10的小鼠身上。这种MPN随着时间的推移演变为AML，表明在没有协同突变的情况下，HOX-过度表达对AML是不够的。我们发现，结构性Shp2激活实现了这一功能。我们假设Triad1是一种白血病抑制因子，可以减少细胞因子刺激的祖细胞的增殖/存活，并且Triad1活性受损促进了疾病的进展/药物 高表达HOX基因AML的耐药性。我们将通过三个目标来实现这一点：目标1：识别与白血病有功能关联的Triad1调节事件。在体外和体内研究Triad1对成纤维细胞生长因子-R1、av？3、Flt3和p53的Ub/降解的影响。目的2：确定在Hox过表达和Shp2激活的AML中Triad1是否是白血病抑制基因。在小鼠AML模型和人AML骨髓样本的研究中，将探索Triad1表达和Shp2激活在耐药/疾病进展中的作用。目的3：明确Triad1抑制白血病的靶向机制。在小鼠模型中，将探讨成纤维细胞生长因子-R1、Flt3、av整合素和p53在白血病发生和耐药中的作用。高表达HOX的AML预后较差，治疗难治。阐明协作性损伤和下游事件可能为这一亚群个体提供治疗靶点。