Genetic Mouse Models of Glioma

描述（申请人提供）：多形性胶质母细胞瘤（GBM）是一种侵袭性的、无法治愈的癌症。这种最常见的恶性脑肿瘤的可怕预后在30年里没有改变。癌症基因组图谱（TCGA）项目对数百个人类GBM样本进行了基因组调查，并确定了一小部分经常发生体细胞突变的基因，包括肿瘤抑制因子NF1、p53和Pten。我们已经生成并研究了自发形成100%发生率的经典GBM的小鼠模型。该模型基于NF1、p53和Pten的体细胞突变。这些肿瘤的完全外显率使我们能够探索早期的肿瘤发生前事件，并确定成体神经干细胞（NSC）生态位是这些肿瘤的主要来源。在之前的资助期内，我们利用这些模型证明了这些肿瘤的干细胞起源，并排除了分化的脑细胞作为来源。我们研究了转录谱，以鉴定胶质瘤特异性的HoxA基因上调，并检查了它们的功能。我们开发了一种工具，通过在自发性胶质瘤中直接谱系追踪，直接测试和证明癌症干细胞（CSCs）在体内的分层群体的存在，而无需诉诸体外移植和/或培养。我们发现了一种新的GBM，它起源于不同的细胞起源。最后，我们开发了一种新的转移性髓母细胞瘤模型，该模型依赖于Dicer突变，目前正在作为一项单独的研究计划进行开发。本建议有两个具体目标。目标1，题为：“胶质瘤中的癌症干细胞：鉴定、分离和表征”，追求我们最近在转基因标记内源性胶质瘤细胞群方面的成功，这些细胞群负责化疗后的肿瘤复发。我们设计了一种先进的NSC和csc特异性转基因，它将共同表达Cre重组酶、eGFP和人白喉毒素受体。这种转基因，当培育成Nf1， p53；如果背景是固定的，则可以更精确地识别和研究相对静止的CSC群体。它将允许纯化用于定量RNA序列分析，并与非csc肿瘤群体和祖细胞NSC群体进行比较。这些研究将为这些新发现的CSCs提供新的信息和见解。目的2将检查“神经祖细胞（npc）和少突胶质细胞祖细胞（OPCs）是否会引起不同形式的胶质瘤和GBM”。我们提供的证据表明，NPCs和OPCs可以通过NF1、p53和Pten的突变引起胶质瘤。突变的npc产生的肿瘤与干细胞区室中产生的肿瘤非常相似，而OPCs产生的是一种独立形式的GBM，具有不同的分子和发育特征。我们建议深入研究这些新肿瘤，因为对病理学家来说，它们属于单一的GBM池。我们对这些肿瘤的详细研究可以为人类肿瘤分析提供信息，并有助于分离这些可能具有不同特性（包括对治疗的反应）的OPC GBMs。这些新型脑肿瘤的基因组学、功能和CSC研究将继续进行。

DESCRIPTION (provided by applicant): Glioblastoma multiforme (GBM) is an aggressive and incurable cancer. The dire prognosis for this most prevalent form of malignant brain tumor is unchanged over 30 years. The Cancer Genome Atlas (TCGA) project has genomically surveyed several hundred human GBM samples and identified a small spectrum of genes that are frequently somatically mutated and include the tumor suppressors NF1, p53 and Pten. We have generated and studied mouse models that spontaneously form classic GBM with 100% incidence. The models are based on somatic mutation of NF1, p53, and Pten. The full penetrance of these tumors has allowed us to probe early pre-tumorigenic events and to identify the adult neural stem cell (NSC) niche as the prevalent source of these tumors. In the previous funding period, we exploited these models to demonstrate a stem cell origin of these tumors and exclude differentiated brain cells as a source. We probed transcriptional profiles to identify glioma-specific upregulation of HoxA genes and examined their function. We developed tools to directly test and demonstrate in vivo the existence of a hierarchical population of cancer stem cells (CSCs) by direct lineage tracing in spontaneous gliomas without resorting to ex vivo transplantation and/or culturing. We unveiled a novel GBM that arises from a different cell of origin. Finally, we developed a novel model of metastatic medulloblastoma that depends on Dicer mutation and is being developed as a separate research initiative. The present proposal embodies two Specific Aims. Aim 1, entitled: "Cancer stem cells in glioma: identification, isolation and characterization." pursues our recent success in transgenically labeling an endogenous glioma cell population that is responsible for tumor recurrence after chemotherapy. We have devised an advanced NSC- and CSC-specific transgene that will co-express Cre recombinase, eGFP, and human diphtheria toxin receptor. This transgene, when bred into the Nf1;p53;Pten floxed background, will permit more precise identification and study of the relatively quiescent CSC population. It will allow purification for quantitative RNA seq analysis i comparison to the non-CSC tumor population, and to the progenitor NSC population. These studies will provide novel information and insight into these newly discovered CSCs. Aim 2 will examine whether "neural progenitor cells (NPCs) and oligodendrocyte progenitor cells (OPCs) give rise to distinct forms of glioma and GBM". We provide evidence that NPCs and OPCs can, by mutations in NF1, p53 and Pten, give rise to gliomas. Mutant NPCs give rise to tumors very similar to the tumors arising in the stem cell compartments whereas OPCs generate an independent form of GBM with distinct molecular, and developmental characteristics. We propose to study these novel tumors in depth since, to the pathologist, they belong to a single GBM pool. Our detailed studies of these tumors may inform human tumor analysis and serve to separate these OPC GBMs that may have different properties, including response to therapies. Genomic, functional, and CSC studies will be pursued for these novel brain tumors.