Hedgehog:YAP:IGF2/mTOR axis in cerebellar precursor division and medulloblastoma

描述（由申请方提供）：髓母细胞瘤是最常见的儿科实体恶性肿瘤。这些肿瘤发生在年幼的儿童从分裂的祖细胞在小脑。目前治疗髓母细胞瘤，手术，颅脊髓放射治疗和化疗，给幸存者留下终身的，毁灭性的副作用。此外，髓母细胞瘤复发和转移是致命的。对引起肿瘤并促进其复发和转移的分子和细胞生物学事件的理解不足，阻碍了新的髓母细胞瘤治疗方法的发展，这些方法使人虚弱程度降低，更有效。更深入地了解基因和蛋白质如何调节小脑祖细胞的增殖，以及它们的失调如何促进肿瘤发生，将确定新疗法的靶点，这些疗法可以特异性地影响肿瘤生长，而不会损害仍在发育的大脑。 髓母细胞瘤分为4-6个遗传亚类。大约30%的髓母细胞瘤与Sonic hedgehog（SHH）通路基因签名相关，该通路的异常激活促进基因工程小鼠模型中的髓母细胞瘤。小脑颗粒神经元前体细胞（CGNP）被认为是SHH髓母细胞瘤的起源细胞，并且它们在发育过程中依赖于SHH进行增殖。在体外，这些细胞（来自新生小鼠）分裂和分化，就像它们在体内一样，因此它们可用于研究信号通路如何在正常脑发育和髓母细胞瘤中调节增殖。使用这样的培养物和小鼠模型，我们发现Shh促进癌基因雅普的活性，这反过来驱动IGF 2的表达，有助于增强增殖并允许肿瘤细胞在辐射中存活，这可能导致肿瘤复发和基因组不稳定。更重要的是，我们发现雅普和IGF 2在人SHH髓母细胞瘤中高度表达。 在提案“Hedgehog：雅普：IGF 2/mTOR轴在小脑前体分裂和髓母细胞瘤”中描述的研究集中于表征这些途径如何相互作用以促进髓母细胞瘤生长和转移。这些研究使用原代CGNP培养物、野生型和Shh髓母细胞瘤荷瘤小鼠的分析以及匿名人类患者样本来研究雅普如何调节IGF 2、IGF 2抑制是否可能是可行的治疗方式、确定Shh髓母细胞瘤生长、复发和转移中对雅普的需求、并检验低氧诱导因子（HIF）位于Shh/IGF介导的mTOR激活的下游并在Shh促有丝分裂和致癌信号传导中起关键作用的假设。这些研究的长期目标是确定如何调节Shh和IGF下游效应物（如雅普和HIF）的功能可能是治疗成神经管细胞瘤和这些通路活跃的其他癌症的有用治疗方法。

DESCRIPTION (provided by applicant): Medulloblastomas are the most common solid pediatric malignant tumors. These tumors arise in young children from dividing progenitor cells in the cerebellum. Current treatments for medulloblastoma, surgery, cranio-spinal radiation, and chemotherapy, leave survivors with life-long, devastating side effects. Moreover, medulloblastoma recurrence and metastasis are lethal. Development of new medulloblastoma therapies that are less debilitating and more effective has been hampered by poor understanding of the molecular and cell biological events causing the tumors and promoting their recurrence and metastasis. Greater insight into how genes and proteins regulate proliferation in cerebellar progenitor cells, and how their dys-regulation contributes to tumorigenesis, will identify targets for new therapies that can specifically affect tumor growth without damaging the still-developing brain. Medulloblastomas are divided into 4-6 genetic subclasses. Approximately 30% of medulloblastomas are associated with a Sonic hedgehog (SHH) pathway genetic signature, and aberrant activation of this pathway promotes medulloblastoma in genetically engineered mouse models. Cerebellar granule neuron precursors (CGNPs) have been proposed as cells of origin for SHH medulloblastomas, and they depend on SHH for proliferation during development. In vitro, these cells (derived from neonatal mice) divide and differentiate much as they do in vivo, hence they are useful for studying how signaling pathways regulate proliferation during normal brain development and in medulloblastomas. Using such cultures and mouse models, we have found that Shh promotes activity of the oncogene YAP, which in turn drives expression of IGF2, contributing to enhanced proliferation and permitting tumor cells to survive radiation, which can lead to tumor recurrence and genomic instability. Importantly, we have shown that YAP and IGF2 are highly expressed in human SHH medulloblastomas. The studies described in the proposal "Hedgehog:YAP:IGF2/mTOR axis in cerebellar precursor division and medulloblastoma" focus on characterizing how these pathways interact to promote medulloblastoma growth and metastasis. These studies use primary CGNP cultures, analysis of wild-type and Shh medulloblastoma-bearing mice, and anonymized human patient samples to investigate how YAP regulates IGF2, whether IGF2 inhibition may be a viable therapeutic modality, determine the requirement for YAP in Shh medulloblastoma growth, recurrence, and metastasis, and test the hypothesis that hypoxia-inducible factor (HIF) lies downstream of Shh/IGF-mediated mTOR activation and plays critical roles in Shh mitogenic and oncogenic signaling. The long-term goal of these studies is to determine how modulating the function of Shh and IGF downstream effectors such as YAP and HIF might be a useful therapeutic approach to treat medulloblastomas and other cancers where these pathways are active.