Glioblastoma Phenotype Modulation Through miRNA Control of Wnt Signaling

 描述（由申请人提供）：胶质母细胞瘤（GBM）是最常见和侵袭性的脑肿瘤，对治疗具有异常耐药性。微小RNA（miRs）是小的非编码RNA，其同时抑制和/或激活多个蛋白质编码基因的表达，并且这样做影响许多细胞行为。Wnt信号通路对机体发育、组织自我更新和修复、肿瘤的发生和发展具有重要意义。在GBM中，miR和Wnt信号转导失调，并导致肿瘤恶性和治疗抗性。胶质瘤干细胞（GSC）是原代胶质瘤的一个细胞亚群，具有干细胞样特性，是胶质瘤复发和治疗耐药的关键因素。我们检查了患者来源的GSC，显示GBM的前神经（PN）和间充质（Mes）样表型，并在每种表型中发现了不同的分子，生物学和治疗反应特征。我们还观察到，相对于Mes样GSC，在PN样GSC中，两种miR，miR-125 b和miR-20 b以相当高的水平表达，并且Wnt信号被富集。体外和体内研究表明，miR-125 b和-20 b调节GSC肿瘤表型。值得注意的是，GSC中存在正反馈环，其中Wnt诱导miR-125 b和-20 b，而miR-125 b/-20 b靶向Wnt抑制剂APC和FZD 6，从而增强Wnt活性。此外，GSC的辐射诱导Mes样表型，减弱Wnt通路，并降低miR-125 b和-20b的水平。基于这些新的观察，我们假设miR-125 b，-20b和Wnt通路在GBM中形成正反馈环，并且这种相互作用调节恶性行为以及辐射诱导的Mes样GBM表型。为了验证这一假设，我们建议1）确定miR-125 b、miR-20 b和Wnt信号传导相互积极影响的机制，并在这样做的过程中影响GSC恶性表型; 2）确定miR-125 b和miR-20 b是否通过Mes相关基因以依赖与独立的方式调节GSC恶性表型，和3）确定miR-125 b/-miR-20 b的调节是否通过Mes相关基因以依赖与独立的方式调节GSC恶性表型。20 b和Wnt信号调节辐射诱导的Mes相关基因表达和表型，并影响GBM肿瘤对治疗的反应。我们的研究将有助于解决现有的缺陷，了解异常的miR表达和Wnt信号活性如何有助于胶质瘤恶性。反过来，这些知识可以导致识别新的靶点和更有效的治疗恶性胶质瘤的疗法。

 DESCRIPTION (provided by applicant): Glioblastomas (GBMs) are the most common and aggressive tumors of the brain with aberrant resistance to therapies. MicroRNAs (miRs) are small non-coding RNAs that simultaneously suppress and/or activate the expression of multiple protein-encoding genes, and in so doing affect numerous cellular behaviors. Wnt pathway is of fundamental importance to development, tissue self-renewal and repair, cancer occurrence and progression. In GBM, miRs and Wnt signaling are dysregulated and contribute to tumor malignancies and therapeutic resistance. Glioma stem cells (GSC) are a cell subpopulation of primary GBM possess stem cell- like properties and is a key factor in glioma tumor recurrence and therapy resistance. We examined patient-derived GSCs displaying proneural (PN)- and mesenchymal (Mes)-like phenotypes of GBM, and found distinct molecular, biological, and therapeutic response characteristics in each. We also observed that in PN-like GSC relative to Mes-like GSC, two miRs, miR-125b and miR-20b are expressed at substantially high levels and that Wnt signaling is enriched. In vitro and in vivo studies demonstrated that miR-125b and -20b modulate GSC tumor phenotypes. Significantly, there is a positive feedback loop in GSC where Wnt induces miR-125b and -20b while miR-125b/-20b target Wnt inhibitors APC and FZD6, enhancing Wnt activity. Moreover, radiation of GSC induced Mes-like phenotypes, attenuated Wnt pathway and decreased levels of miR-125b and -20b. Based on these novel observations, we hypothesize that miR-125b, -20b and Wnt pathway form a positive feedback loop in GBM, and this interaction regulates malignant behaviors as well as radiation-induced Mes-like GBM phenotypes. To test this hypothesis, we propose to 1) define mechanisms by which miR-125b, miR-20b and Wnt signaling positively influence each other, and in so doing affect GSC malignant phenotypes; 2) determine whether miR-125b and miR-20b regulates GSC malignant phenotypes through Mes- associated genes in a dependent vs. an independent manner and 3) determine whether modulation of miR-125b/-20b and Wnt signaling regulates radiation-induced Mes-associated gene expression and phenotypes, and affects GBM tumor response to therapies. Our studies will help address an existing deficiency in understanding of how aberrant miR expression and Wnt signaling activity contribute to glioma malignancy. This knowledge, in turn, could lead to the identification of novel targets and more effective therapies for treating malignant gliomas.