Investigating Cancer Stem Cells - Niche Interactions in Brain Tumor

描述（申请人提供）：胶质母细胞瘤（Glioblastoma， GBM）是人类最常见的恶性脑肿瘤，预后极差。这种致命疾病迫切需要新的治疗策略。肿瘤干细胞样细胞（CSLCs）有望从GBM中分离出来，并被证明是肿瘤增殖所必需的。然而，研究表明，GBM CSLCs存在于生态位（包括内皮生态位）中，并且对化疗和放疗具有耐药性。了解壁龛细胞和CSLCs之间的分子通讯将有助于开发基于CSLCs及其壁龛的GBM患者的新治疗策略。我们的长期目标是通过研究信号通路和肿瘤微环境调控GBM中CSLCs的分子机制，为GBM患者开发新的治疗策略。我们和其他人最近已经证明，用γ分泌酶抑制剂（GSI）阻断Notch通路可以消耗GBM CSLCs，抑制肿瘤生长，并延长颅内异种移植物小鼠的存活时间。本应用程序的总体目标是确定GBM CSLCs中获得性Notch活性是否来自内皮细胞和分化肿瘤细胞（小生境细胞）中表达的Notch配体，研究Notch信号在其小生境中调节GBM CSLCs的分子机制，并在临床前模型中研究靶向GBM CSLCs和小生境细胞是否可以改善GBM的治疗。在特定的Aim1中，我们将研究Notch配体在壁龛细胞（内皮细胞和分化的肿瘤细胞）中的表达是否有助于Notch在GBM CSLCs中的激活。我们将首先确定哪些Notch配体在原发性GBM样本的内皮细胞和分化肿瘤细胞中表达。然后，我们将在体外和体内研究敲低小生境细胞中的Notch配体是否会降低共培养GBM CSLCs的生长。在特定的Aim2中，我们将定义配体诱导的Notch激活调节GBM CSLCs的分子机制。我们将使用notch功能的获得和缺失研究来确定介导GBM CSLCs中notch调节的增殖、凋亡和分化的靶点。在特定的目标3中，我们将在临床前小鼠模型中研究靶向CSLCs及其生态位是否会改善GBM的治疗。我们将研究GSI靶向GBM CSLCs和VEGF抑制剂（Avastin）靶向内皮细胞生态位的组合是否会提高人原发性GBMs颅内异种移植物小鼠的存活率。本研究的成功不仅将增强我们对GBM CSLCs及其利基之间分子通讯的理解，而且将有助于开发基于CSLCs及其利基的GBM患者的新疗法。虽然目前的研究主要集中在GBM，但这些结果也将对多种形式的瘤变具有普遍意义。

DESCRIPTION (provided by applicant): Glioblastoma (GBM) is the most common malignant brain tumor in human with extremely poor prognosis. Novel treatment strategies to this deadly disease are desperately needed. Cancer stem-like cells (CSLCs) have been prospectively isolated from GBM and shown required for tumor propagation. However, it has been shown that GBM CSLCs reside within niches (including endothelial niche) and are resistant to chemo- and radiation-therapy. Understanding the molecular communication between niche cells and CSLCs will help develop novel therapeutic strategies for GBM patients based on targeting both CSLCs and their niches. Our long-term goal is to develop novel therapeutic strategies for GBM patients through investigating the molecular mechanism by which signaling pathways and tumor microenvironment regulate CSLCs in GBM. We and others have demonstrated recently that Notch pathway blockade with a gamma-secretase inhibitor (GSI) depletes GBM CSLCs, inhibits tumor growth, and prolongs survival of mice bearing intracranial xenografts. The overall objective of this application is to define if acquired Notch activity in GBM CSLCs comes from Notch ligands expressed in endothelium and differentiated tumor cells (niche cells), to study the molecular mechanism by which Notch signaling regulates GBM CSLCs within their niches, and to investigate if targeting both GBM CSLCs and niche cells can improve the treatment of GBM in a pre-clinical model. In specific Aim1, we will examine if Notch ligands expressed in niche cells (endothelial cells and differentiated tumor cells) contribute to the activation of Notch in GBM CSLCs. We will first identify which Notch ligands are expressed in endothelial cells and differentiated tumor cells in primary GBM samples. Then, we will examine if knockdown of Notch ligands in niche cells will reduce growth of co-cultured GBM CSLCs in vitro and in vivo. In specific Aim2, we will define the molecular mechanism by which ligand-induced Notch activation regulates GBM CSLCs. We will use both gain and loss of Notch-function studies to identify the targets that mediate Notch-regulated proliferation, apoptosis, and differentiation in GBM CSLCs. In specific Aim3, we will examine if targeting both CSLCs and their niche will improve the treatment of GBM in a pre-clinical mouse model. We will examine if a combination targeting GBM CSLCs by GSI and targeting endothelial cell niche by VEGF inhibitor (Avastin) will improve survival of mice bearing intracranial xenografts derived from human primary GBMs. Success in the current proposal will not only enhance our understanding the molecular communication between GBM CSLCs and their niche, but will also help develop novel therapies for GBM patients based on targeting both CSLCs and their niches. Although the current research focuses on GBM, such results will also have general implications for multiple forms of neoplasia.