Investigating Cancer Stem Cells - Niche Interactions in Brain Tumor

描述（由申请人提供）：胶质母细胞瘤（GBM）是人类最常见的恶性脑肿瘤，预后极差。 迫切需要针对这种致命疾病的新治疗策略。 癌症干细胞样细胞（CSLC）已被前瞻性地从GBM中分离出来，并显示为肿瘤增殖所需。 然而，已经显示GBM CSLC驻留在小生境（包括内皮小生境）内，并且对化疗和放疗具有抗性。 了解小生境细胞和CSLCs之间的分子通讯将有助于基于靶向CSLCs及其小生境为GBM患者开发新的治疗策略。 我们的长期目标是通过研究信号通路和肿瘤微环境调节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通路可以耗尽GBM CSLC，抑制肿瘤生长，并延长颅内异种移植小鼠的存活时间。 本申请的总体目的是确定GBM CSLC中获得的Notch活性是否来自内皮和分化的肿瘤细胞（小生境细胞）中表达的Notch配体，研究Notch信号传导调节其小生境内的GBM CSLC的分子机制，并研究靶向GBM CSLC和小生境细胞两者是否可以改善临床前模型中GBM的治疗。 在特定的Aim 1中，我们将检查在小生境细胞（内皮细胞和分化的肿瘤细胞）中表达的Notch配体是否有助于GBM CSLC中Notch的活化。 我们将首先鉴定哪些Notch配体在原代GBM样品中的内皮细胞和分化的肿瘤细胞中表达。 然后，我们将检查敲低小生境细胞中的Notch配体是否会在体外和体内减少共培养的GBM CSLC的生长。 在特定的Aim 2中，我们将定义配体诱导的Notch激活调节GBM CSLC的分子机制。 我们将使用Notch功能的获得和丧失研究来确定介导Notch调节的GBM CSLC增殖、凋亡和分化的靶点。 在特定的Aim 3中，我们将检查靶向CSLC及其生态位是否会改善临床前小鼠模型中GBM的治疗。 我们将检查通过GSI靶向GBM CSLC和通过VEGF抑制剂（Avastin）靶向内皮细胞龛的组合是否会改善携带源自人原发性GBM的颅内异种移植物的小鼠的存活。 当前提案的成功不仅将增强我们对GBM CSLC及其生态位之间分子通讯的理解，而且还将有助于基于靶向CSLC及其生态位为GBM患者开发新的疗法。 虽然目前的研究重点是GBM，但这些结果也将对多种形式的瘤形成产生普遍影响。

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.