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，并基于Notch通路抑制开发新的脑肿瘤治疗方法。Notch受体控制着大脑中干细胞和祖细胞的分化、增殖和存活。Notch信号也与肿瘤发生有关，包括髓母细胞瘤和胶质瘤等脑肿瘤的形成和生长。我们最近发现Notch2基因在原发性髓母细胞瘤/PNET中被扩增和过表达，并促进髓母细胞瘤细胞系的生长。相反，NotcM抑制成神经管细胞瘤细胞的增殖。我们是第一个确定两个Notch受体具有相反作用的体外系统的小组。我们将在Notch 1和Notch2之间建立嵌合体，并利用这个系统来确定Notch的哪些结构域对增殖和分化有差异调节（Aim I）。这应该为Notch信号的机制提供基本的见解，也有助于指导我们开发新的治疗方法。为了通过Notch调节有效地治疗脑肿瘤，理解通路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Aim II中，我们将确定配体刺激和受体突变在髓母细胞瘤Notch通路激活中的作用。第三个目的是评估Notch通路阻断对肿瘤干细胞和肿瘤增殖的影响。我们已经证明Notch通路阻断在体外抑制成神经管细胞瘤的增殖和诱导细胞凋亡。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。肿瘤细胞的这一亚群似乎在脑肿瘤的传播中起着至关重要的作用，起着“肿瘤干细胞”的作用。因此，靶向治疗引起肿瘤干细胞分化或死亡是一种极具前景的新型治疗途径。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，Nbtch2的持续激活是否足以启动成神经管细胞瘤的形成尚不清楚。在Aim IV中，我们将激活的Notch2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.