The effects of the unfolded protein response on medulloblastoma

描述(申请人提供)：髓母细胞瘤(MB)是一种高度恶性的儿童脑肿瘤，5年生存率约为60%。多种信号通路，如Sonic hedgehog(SHH)通路，与MB肿瘤的发生有关。然而，人们对MB侵袭和血管生成的调控机制知之甚少。越来越多的证据表明，肿瘤微环境激活的未折叠蛋白反应(UPR)在肿瘤的发生发展中起着重要作用。UPR的胰腺内质网激酶(PERK)分支的激活抑制了整体蛋白质的生物合成，但通过磷酸化翻译起始因子21(EIF21)来刺激某些应激诱导基因的表达，如血管内皮生长因子A(VEGF)。研究表明，肿瘤细胞来源的血管内皮生长因子不仅能促进血管生成，还能以自分泌的方式直接作用于肿瘤细胞，促进肿瘤的生长和侵袭。有趣的是，最近的一项研究表明，血管内皮生长因子在MB生长中可能起着自分泌作用。我们以前的研究表明，在发育过程中，干扰素-3在中枢神经系统的强制表达会导致小脑发育不良或MB。重要的是，我们的初步数据表明，PERK-eIF21通路的激活促进了干扰素-3诱导的MB的形成。因此，在这项提案中，我们将检验这样的假设，即UPR的PERK分支通过诱导血管内皮生长因子(VEGF)促进肿瘤细胞的侵袭和血管生成，促进MB的发展，并使MB细胞对化疗产生耐药性。在第一个特定目标中，我们将使用遗传方法操纵PERK-eIF21途径的活性，以确定UPR是否影响SHH受体Patched1杂合缺陷小鼠的MB形成。我们还将评估PERK-eIF21通路对血管生成、肿瘤细胞侵袭和增殖以及肿瘤中血管内皮生长因子表达的影响。在第二个特定目标中，我们将利用体外细胞培养来确定PERK-eIF21通路的激活是否通过诱导血管内皮生长因子来促进MB细胞的迁移和侵袭。此外，我们将利用小脑内MB异种移植模型，确定在MB细胞中，PERK信号的促肿瘤形成作用是否由自分泌的VEGF/VEGF受体2信号介导。在最终的具体目标中，我们将确定在人类患者的MB中是否激活了UPR。此外，我们还将探讨PERK-eIF21通路在MB化疗耐药中的作用及其潜在机制。这项拟议工作的意义在于，它将揭示导致MB侵袭、血管生成和化疗耐药的新机制。从这些研究中获得的知识将对MB肿瘤的发生有重要的影响，并可能导致治疗这种疾病的新的治疗策略。

DESCRIPTION (provided by applicant): Medulloblastoma (MB) is a highly malignant pediatric brain tumor with a 5-year survival rate of ~ 60%. Multiple signaling pathways, such as the sonic hedgehog (SHH) pathway, have been associated with MB tumorigenesis. Nevertheless, little is known about the mechanisms that regulate MB invasion and angiogenesis. Evidence is emerging that the unfolded protein response (UPR) activated in response to the tumor microenvironment plays a role in tumor development. Activation of the pancreatic endoplasmic reticulum kinase (PERK) branch of the UPR inhibits global protein biosynthesis, but stimulates the expression of certain stress-induced genes, such as vascular endothelial growth factor A (VEGF), by phosphorylating translation initiation factor 21 (eIF21). Data indicate that tumor cell-derived VEGF not only enhances angiogenesis but also acts directly on tumor cells in an autocrine manner to promote tumor growth and invasion. Interestingly, a recent study suggested a possible autocrine role of VEGF in MB growth. Our previous studies showed that enforced expression of interferon-3 in the central nervous system during development led to cerebellar dysplasia or MB. Importantly, our preliminary data suggested that activation of the PERK-eIF21 pathway facilitated interferon-3-induced MB formation. Thus, in this proposal, we will test the hypothesis that the PERK branch of the UPR promotes MB development by enhancing the tumor cell invasion and angiogenesis through the induction of VEGF, and renders MB cells resistant to chemotherapy. In the first specific aim, we will manipulate the activity of the PERK-eIF21 pathway using genetic approaches to determine whether the UPR influences MB formation in mice with heterozygous deficiency of patched1, a SHH receptor. We will also assess the effects of the PERK-eIF21 pathway on angiogenesis, tumor cell invasion and proliferation, and the expression of VEGF in the tumors. In the second specific aim, we will determine whether activation of the PERK-eIF21 pathway promotes MB cell migration and invasion through the induction of VEGF utilizing in vitro cell cultures. Moreover, we will determine whether the pro-tumorigenesis actions of PERK signaling are mediated by autocrine VEGF/VEGF receptor 2 signaling in MB cells utilizing an intracerebellar MB xenograft model. In the final specific aim, we will determine whether the UPR is activated in MB in human patients. Additionally, we will explore the role of the PERK-eIF21 pathway in MB resistance to chemotherapy and its underlying mechanisms. The significance of this proposed work is that it will uncover a novel mechanism responsible for MB invasion, angiogenesis, and chemotherapy resistance. The knowledge gained from these studies will have important implications for MB tumorigenesis and may lead to novel therapeutic strategies for treating this disease.