Mechanisms of ID2 regulation in glioma

摘要 维持癌症干细胞的机制对肿瘤的进展至关重要。ID蛋白是支持 恶性胶质瘤和其他肿瘤类型的干性、组织侵袭和血管生成。在ID蛋白中，ID2 有助于癌症的标志，促进神经肿瘤的化疗耐药性，是基因签名的一部分， 预测高级别胶质瘤患者的不良预后。低氧诱导因子(HIF)，最显著的 HIF2在肿瘤干细胞中表达，是维持肿瘤干细胞所必需的。然而，这些路径是 在肿瘤进展过程中，Id2参与或驱动HIF2积聚的机制尚不清楚。在这份提案中， 我们将继续我们最新的工作，重建了ID2和ID2激活之间的分子事件 HIF2在癌症中的表达升高。我们的工作表明，VHL-Elongin C-Elongin B(VCB)-Cul2的破坏 未磷酸化的Id2-Thr-27复合体是HIF2在干细胞中稳定的重要机制 胶质瘤干细胞(GSCs)诱导的DYRK1对ID2活性的抑制作用 常氧条件下的激酶激活和ID2-Thr-27的磷酸化。有趣的是，ID2-T27A突变体 结构性地使vcb-cul2失活，升高缺氧诱导因子，并维持癌症干细胞。在提案中，我们将 一种新的肿瘤抑制途径PHD-DYRK1活性的生化和功能表征 抑制活性ID2对VCB-Cul2泛素连接酶的干扰作用。在目标1中，我们将确定ID2- PT27磷酸酶，一个潜在的癌蛋白，并阐明Thr-27磷酸化在 ID2互动组。Phd1-DYRK1-ID2-HIF2通路在脑胶质瘤进展中的生物学意义 利用PHD1Flox小鼠，我们将机械地剖析组成ID2的功能 在体内没有PhD1的情况下激活。我们还将模拟VHL失活、HIF稳定和 ID2-T27A突变在携带突变ID2的敲入等位基因的可诱导小鼠模型中的胶质瘤形成。 我们将利用这只小鼠来验证ID2-T27A对VHL和VHL的生化和生物学效应。 体内HIF-。小鼠模型也将被用于确定ID2-T27A是否促进胶质瘤的进展 与已知在人类癌症中与ID2合作的其他肿瘤特异性突变。研究 将解决癌症生物学中的基本问题，并极大地增强对如何标记 ID2对神经胶质瘤进展的影响。最后，Id2-Vh1-Hif-轴对人类的意义 疾病将在患者来源的GSCs和原发的GBM中进行测试。

Abstract Mechanisms that maintain cancer stem cells are crucial to tumor progression. ID proteins are essential to support stemness, tissue invasion and angiogenesis in malignant glioma and other tumor types. Among ID proteins, ID2 contributes to cancer hallmarks, promotes chemoresistance of neural tumors and is part of a gene signature that predicts poor outcome in patients with high-grade glioma. Hypoxia–Inducible Factors (HIFs), most notably HIF2, are expressed in and required for maintenance of cancer stem cells. However, the pathways that are engaged by ID2 or drive HIF2 accumulation during tumor progression have remained unclear. In this proposal, we will follow on our most recent work that has reconstructed the molecular events linking activation of ID2 and elevation of HIF2 in cancer. Our work indicates that disruption of the VHL-Elongin C-Elongin B (VCB)-Cul2 complex by un-phosphorylated ID2-Thr-27 is an important mechanism of HIF2 stabilization in stem cells and glioma stem cells (GSCs) and that ID2 activity is restrained by prolyl hydroxylase 1 (PHD1)-induced DYRK1 kinase activation and ID2-Thr-27 phosphorylation under normoxic conditions. Interestingly an ID2-T27A mutant constitutively inactivates VCB-Cul2, elevates HIF and maintains cancer stem cells. In the proposal, we will characterize biochemically and functionally PHD-DYRK1 activity, a new tumor suppressor pathway that operates by restraining the interfering effect of active ID2 on VCB-Cul2 ubiquitin ligase. In Aim 1 we will identify the ID2- pT27 phosphatase, a potential oncoprotein and elucidate the broad significance of Thr-27 phosphorylation for the ID2 interactome. The biological implication of the PHD1-DYRK1-ID2-HIF2 pathway for glioma progression will be explored in Aim 2. Using PHD1Flox mice we will mechanistically dissect the function of constitutive ID2 activation in the absence of PHD1 in vivo. We will also model VHL inactivation, HIF stabilization and gliomagenesis by ID2-T27A mutation in an inducible mouse model harboring a knock-in allele of the mutant ID2. We will use this mouse to validate the biochemical and biological effects of ID2-T27A that converge on VHL and HIF in vivo. The mouse model will also be used to determine whether ID2-T27A promotes glioma progression in cooperation with other tumor-specific mutations that are known to cooperate with ID2 in human cancer. Studies will address fundamental questions in cancer biology and greatly enhance the understanding of how hallmarks of glioma progression are effected by ID2. Finally, the significance of the ID2-VHL-HIF-axis for the human disease will be tested in patient-derived GSCs and primary GBM.