Mechanisms of ID2 regulation in glioma

摘要 维持癌症干细胞的机制对肿瘤进展至关重要。ID蛋白质对于支持 恶性胶质瘤及其它肿瘤类型中干细胞、组织浸润和血管生成。在ID蛋白中，ID2 有助于癌症标志，促进神经肿瘤的化学抗性，并且是基因签名的一部分， 预测高级别胶质瘤患者预后不良。缺氧诱导因子（HIF），最明显的是 HIF 2在癌症干细胞中表达，并且是维持癌症干细胞所需的。然而， 在肿瘤进展过程中，ID2参与或驱动HIF 2 α积累的研究仍不清楚。在这一提议中， 我们将继续我们最近的工作，重建了与ID2激活相关的分子事件， 癌症中HIF 2 α的升高。我们的工作表明，VHL-延伸蛋白C-Elongin B（VCB）-Cul2的破坏 未磷酸化的ID2-Thr-27复合物是干细胞中HIF 2 α稳定化的重要机制， 神经胶质瘤干细胞（GSC）和ID2活性受到脯氨酰羟化酶1（PHD1）诱导的DYRK1抑制 激酶活化和ID2-Thr-27磷酸化。有趣的是，ID2-T27A突变体 组成型失活VCB-Cul2，提高HIF-1 α并维持癌症干细胞。在提案中，我们将 表征生物化学和功能PHD-DYRK1活性，一种新的肿瘤抑制途径， 抑制活性ID2对VCB-Cul2泛素连接酶的干扰作用。在目标1中，我们将识别ID2- pT27磷酸酶，一种潜在的癌蛋白，并阐明了Thr-27磷酸化对 ID2基因组PHD1-DYRK1-ID2-HIF 2 α通路在胶质瘤进展中的生物学意义 将在目标2中探讨。使用PHD 1 Flox小鼠，我们将机械地剖析组成性ID 2的功能 在体内PHD1不存在下的活化。我们还将模拟VHL失活、HIF-1 α稳定和 在携带突变体ID2的敲入等位基因的诱导型小鼠模型中通过ID2-T27A突变的胶质瘤发生。 我们将使用这只小鼠来验证ID 2-T27 A的生化和生物学效应，这些效应聚集在VHL上， 体内HIF表达。小鼠模型还将用于确定ID2-T27 A是否促进神经胶质瘤进展 与已知在人类癌症中与ID2合作的其他肿瘤特异性突变合作。研究 将解决癌症生物学中的基本问题，并极大地提高对癌症标志物 胶质瘤的进展受ID2的影响。最后，我们对ID2-VHL-HIF-γ轴在人类肿瘤中的意义进行了初步探讨。 将在患者来源的GSC和原发性GBM中测试疾病。

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.