Hypoxia Regulates Notch Turnover in Glioma Stem Cells Through Vasorin

 描述（由申请人提供）：癌症干细胞驻留在缺氧区域并促进肿瘤进展。这些细胞特别难以治疗，因为它们固有地对常规疗法具有抗性，并且它们的微环境降低了辐射的功效并损害了化疗的递送。胶质母细胞瘤是一种无法治愈的原发性脑肿瘤，其特征在于缺氧区域。Notch信号维持GSC在缺氧生态位内，但Notch如何失调尚不清楚。 我们的初步数据强烈表明，缺氧可以调节膜Notch水平，从而调节受体的配体结合的可用性。我们发现最近鉴定的低氧调节蛋白Vasorin优先在GSC中表达以调节Notch信号传导。我们的数据表明，Vasorin通过抑制Notch 1的溶酶体降解来调节GSC的自我更新。因此，我们已经确定了一种新的机制，缺氧指导Notch信号：受体周转的调节。 我们的中心假设是Vasorin通过调节Notch信号传导来调节GSC在缺氧小生境中的自我更新，并且靶向Vasorin可以改善GBM治疗。我们将通过机制和临床前研究来验证我们的假设。在目的1中，我们将确定Vasorin在体外和体内介导GSC特性和致瘤潜力中的作用。在目标2中，我们将定义Vasorin在调节Notch信号以促进低氧条件下GSC自我更新中的作用。在目标3中，我们将评估Vasorin作为预后生物标志物，并提供通过Vasorin和Notch蛋白水解加工的双重靶向最大化Notch抑制可以改善胶质母细胞瘤小鼠模型的存活率的原理证明。重要的是，Vasorin似乎在正常胚胎或成人大脑中不表达。因此，靶向Vasorin可能具有有限的正常脑毒性。 这些数据将揭示Vasorin在调节Notch信号传导中的重要作用，并具有重要的临床意义。目前使用缺氧调节剂或Notch途径抑制剂（如β-分泌酶抑制剂）的疗法受到副作用的限制。如果成功，这项研究的结果将为开发针对Vasorin的新疗法提供强有力的理论基础。

 DESCRIPTION (provided by applicant): Cancer stem cells reside in hypoxic areas and contribute to tumor progression. These cells are particularly difficult to treat because they are inherently resistant to conventional therapy, and their microenvironment reduces the efficacy of radiation and impairs delivery of chemotherapy. Glioblastoma is an incurable primary brain tumor that is characterized by regions of hypoxia. Notch signaling maintains GSCs within the hypoxic niche, but how Notch is dysregulated is unclear. Our preliminary data strongly suggest that hypoxia can regulate membranous Notch levels, thereby regulating receptor availability for ligand binding. We have found that the recently identified hypoxia-regulated protein, Vasorin, is preferentially expressed in GSCs to regulate Notch signaling. Our data suggest that Vasorin regulates GSC self-renewal by inhibiting the lysosomal degradation of Notch1. Thus, we have identified a novel mechanism by which hypoxia directs Notch signaling: regulation of receptor turnover. Our central hypothesis is that Vasorin regulates GSC self-renewal within the hypoxic niche by regulating Notch signaling and that targeting Vasorin may improve GBM therapy. We will test our hypothesis through mechanistic and preclinical studies. In Aim 1, we will determine the role of Vasorin in mediating GSC properties and tumorigenic potential in vitro and in vivo. In Aim 2, we will define the role of Vasorin in regulating Notch signaling to promote GSC self-renewal under hypoxic conditions. In Aim 3, we will assess Vasorin as a prognostic biomarker and provide proof-of-principle that maximizing Notch inhibition by dual targeting of Vasorin and Notch proteolytic processing can improve survival in mouse models of glioblastoma. Importantly, Vasorin does not appear to be expressed in normal embryonic or adult brain. Therefore, targeting Vasorin may have limited normal brain toxicity. These data will reveal an important role for Vasorin in regulating Notch signaling and have significant clinical ramifications. Current therapies using hypoxia modifiers or Notch pathway inhibitors, such as -secretase inhibitors, are limited by side effects. If successful, the findings of this study will provide a strong rationale for the development of novel therapeutics against Vasorin.