Notch signaling in brain tumors

描述（由申请人提供）：本提案的目标是确定Notch信号通路如何调节脑肿瘤的形成和生长，并开发基于Notch通路抑制的新的脑肿瘤疗法。Notch受体控制脑中干细胞和祖细胞的特化、增殖和存活。Notch信号传导还涉及肿瘤发生，包括脑肿瘤如成神经管细胞瘤和神经胶质瘤的形成和生长。我们最近发现Notch 2基因在原发性髓母细胞瘤/PNET中扩增和过表达，并促进髓母细胞瘤细胞系的生长。相反，NotcM抑制髓母细胞瘤细胞增殖。我们是第一个定义两种Notch受体具有相反作用的体外系统的小组。我们将创建Notch 1和Notch 2之间的嵌合体，并利用该系统来确定Notch的哪些结构域差异调节增殖和分化（目的I）。这将为Notch信号传导机制提供基本见解，并有助于指导我们开发新疗法。为了通过Notch调节有效地治疗脑肿瘤，了解该途径开启的机制也很重要，因为它必须在激活水平或低于激活水平时被阻断。因此，在目的II中，我们将确定配体刺激和受体突变在髓母细胞瘤中激活Notch通路的作用。第三个目的是评估Notch途径阻断对肿瘤干细胞和肿瘤增殖的影响。我们已经证明Notch通路阻断抑制体外髓母细胞瘤的增殖并诱导其凋亡。最近，从新鲜切除的人髓母细胞瘤/PNET中分离出具有干细胞样特性的细胞。这种肿瘤细胞的亚群在脑肿瘤的增殖中似乎是至关重要的，其功能是“肿瘤干细胞”。“因此，导致肿瘤干细胞分化或死亡的靶向治疗代表了一种具有巨大前景的新治疗途径。我们假设Notch通路在正常胎儿发育过程中控制神经干细胞的存活和增殖，也是肿瘤干细胞存活所必需的，并将在Aim III中对此进行测试。最后，目前还不清楚Nbtch 2的持续激活是否足以启动髓母细胞瘤的形成。在目的IV中，我们将激活Notch 2引入小脑前体细胞并评估其转化能力。

DESCRIPTION (provided by applicant): The goal of this proposal is to determine how the Notch signaling pathway regulates the formation and growth of brain tumors, and to develop new brain tumor therapies based on Notch pathway inhibition. Notch receptors control the specification, proliferation and survival of stem and progenitor cells in the brain. Notch signaling is also implicated in tumorigenesis, including the formation and growth of brain tumors such as medulloblastoma and glioma. We have recently shown that the Notch2 gene is amplified and overexpressed in primary medulloblastoma/PNET, and promotes growth of medulloblastoma cell lines. In contrast, NotcM inhibits medulloblastoma cell proliferation. We are the first group to define an in vitro system in which two Notch receptors have opposing effects. We will create chimeras between Notch 1 and Notch2 and exploit this system to determine which domains of Notch differentially regulate proliferation and differentiation (Aim I). This should provide basic insights into the mechanism of Notch signaling, and also help guide our development of new therapies. To effectively treat brain tumors via Notch modulation, it will also be important to understand the mechanisms by which the pathway is turned on, as it must be blocked at or below the level of activation. In Aim II, we will therefore determine the roles of ligand stimulation and receptor mutation in activating the Notch pathway in medulloblastoma. A third aim is to assess the effects of Notch pathway blockade on tumor stems cells and tumor propagation. We have already shown that Notch pathway blockade inhibits proliferation and induces apoptosis of medulloblastoma in vitro. Recently, cells with stem- like properties have been isolated from freshly resected human medulloblastoma/PNET. This subset of neoplastic cells appears to be critical in propagating brain tumors, functioning as "tumor stem cells." Targeted therapies causing tumor stem cells to differentiate or die therefore represent a novel therapeutic avenue with great promise. We hypothesize that the Notch pathway, which controls neural stem cell survival and proliferation during normal fetal development, will also be required for tumor stem cells survival, and will test this in Aim III. Finally, it is not known if persistent activation of Nbtch2 is sufficient to initiate the formation of medulloblastoma. In Aim IV, we will introduce activated Notch2 into cerebellar precursor cells and assess its transforming capacity.