METABOLISM IN HUMAN GLIOMAS

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 胶质母细胞瘤是成人中最常见的原发性脑肿瘤，被认为是人类最致命的癌症之一。中位生存时间为14.6个月，在最积极的治疗方案后约25%的患者存活2年，显然迫切需要提高对这种疾病基本生物学过程的理解。胶质母细胞瘤表现出不受调节的增殖、对细胞凋亡的抗性和诱导新血管形成的经典癌症表型。在临床上，胶质母细胞瘤在FDG-PET上是“热的”，表现出明显的葡萄糖摄取异常，被认为反映了“瓦尔堡现象”，其定义为尽管有完整的三羧酸（TCA）循环，但通过无氧糖酵解产生乳酸的葡萄糖过量通量。相比之下，低级别胶质瘤是生长缓慢的肿瘤，FDG-PET显示葡萄糖摄取没有增加，直到它们进展为胶质母细胞瘤，这种转变发生在初次诊断后5-10年内。目前尚不清楚代谢的变化是否仅仅反映了细胞增殖显著增加导致的葡萄糖利用率增加，或者是控制从低级别胶质瘤向胶质母细胞瘤转变的分子开关的直接结果。 胶质母细胞瘤潜在的分子畸变在基因组水平上得到了很好的表征，包括拷贝数变化、突变和甲基化，并与转录组的变化相关。从这些数据中，已经出现了涉及胶质母细胞瘤生长和存活的关键癌症途径的重要框架，主要集中在RAS-MAPK途径的激活，最常见的是由EGFR扩增驱动，以及PI 3激酶途径的失调，通常是由于PTEN的缺失。 DNA修复基因MGMT的甲基化可以预测对烷化剂治疗的反应，最近发现的异柠檬酸脱氢酶1（IDH 1）突变可以调节代谢途径，但总体而言，分子变化和改变的生化途径如何影响胶质母细胞瘤的生物学仍然存在有限的观点。 在胶质母细胞瘤中，与大多数实体瘤一样，人们对理解代谢改变的机制非常感兴趣，因为它代表了相互作用以影响细胞生长和存活的基因突变星座的“功能读数”。为了开发基于代谢改变的新的诊断方法和治疗靶点，必须解决与基因型-代谢表型连接相关的基本问题。此外，我们认为，关键是要了解破坏的生化途径对代谢产物（如厌氧糖酵解中产生的乳酸）的静态浓度以及通过相关途径（如糖酵解、磷酸戊糖途径和柠檬酸循环）的通量的影响。胶质母细胞瘤的特征和公认的代谢特征  FDG扫描显示葡萄糖摄取强烈，乳酸产生丰富， NADP+依赖性异柠檬酸脱氢酶  可能是由于特定的基因突变而相互关联的事件。或者，这些特征可能是反映癌细胞遗传程序冗余的共同终点。 假设声明：RAS-MAPK途径的激活和/或PI 3激酶途径的失调刺激胶质母细胞瘤细胞中葡萄糖摄取增加和代谢变化级联，其维持高增殖速率并支持异质肿瘤微环境中的广泛细胞浸润/迁移。 目标1：通过输注[U-13 C]葡萄糖或[1，2 - 13 C]葡萄糖后对肿瘤进行13 C NMR光谱分析，分别评估柠檬酸循环中交叉的途径和通过磷酸戊糖途径的相对通量，确定新型人原位小鼠模型中胶质母细胞瘤的代谢表型。 目标二：在基因工程胶质母细胞瘤小鼠模型中，确定EGFR过表达引起的Ras-MAPK通路激活和PTEN缺失引起的PI 3 K通路失调对代谢表型的影响。 目标3：确定胶质母细胞瘤小鼠模型中IDH 1的调节是否改变通过柠檬酸循环或磷酸戊糖途径的通量。 目的4：将目的1-3中的发现与胶质母细胞瘤患者的代谢研究相关联。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Glioblastoma, the most common primary brain tumor in adults, is considered to be among the deadliest of human cancers. With a median survival time of 14.6 months and approximately 25% of patients alive at 2 years after the most aggressive treatment regimens, there is clearly a desperate need to improve the understanding of basic biological processes in this disease. Glioblastomas demonstrate the classic cancer phenotype of unregulated proliferation, resistance to apoptosis, and induction of neovascularization. Clinically, glioblastomas are 'hot' on FDG-PET, demonstrating marked abnormal uptake of glucose, thought to reflect the 'Warburg phenomenon', defined as excess flux of glucose through anaerobic glycolysis with production of lactate despite an intact tricarboxylic acid (TCA) cycle. In contrast, low grade gliomas, which are slow growing tumors, show no increase in glucose uptake by FDG-PET until they progress to glioblastoma, a transition that occurs within 5-10 years of initial diagnosis. It is unknown whether the change in metabolism simply reflects an increased rate of glucose utilization as a result of the marked increase in cellular proliferation or is a direct consequence of a molecular switch that governs the transition from low grade glioma to glioblastoma. The molecular aberrations underlying glioblastoma have been well characterized at the level of the genome, including copy number changes, mutations, and methylation, and correlated with changes in the transcriptome. From these data an important framework of critical cancer pathways involved in glioblastoma growth and survival has emerged, centered predominantly on activation of the RAS-MAPK pathway, most commonly driven by EGFR amplification, and dysregulation of the PI3Kinase pathway, due frequently to deletion of PTEN. Methylation of the DNA repair gene, MGMT, may predict for response to alkylator therapy and the recently identified mutation in isocitrate dehydrogenase 1 (IDH1) may modulate a metabolic pathway but, overall, there remains a limited view of how the molecular changes and altered biochemical pathways influence the biology of glioblastoma. In glioblastoma, as in most solid tumors, there is significant interest in understanding mechanisms of altered metabolism since it represents a 'functional readout' of the constellation of genetic mutations that interact to influence cell growth and survival. In order to develop new diagnostic methods and therapeutic targets based on altered metabolism, it is imperative that basic questions related to the genotype-metabolic phenotype connection be addressed. Further, we believe it is critical to understand the effects of disrupted biochemical pathways on both the static concentration of metabolites such as lactate produced in anaerobic glycolysis, as well as fluxes through relevant pathways such as glycolysis, the pentose phosphate pathway, and the citric acid cycle. The characteristic and well established metabolic features of glioblastoma  intense glucose uptake on FDG scans, abundant lactate production, and a defect in NADP+ - dependent isocitrate dehydrogenase  may be interconnected events due to a specific genetic mutation. Alternatively, these features may be a common endpoint reflecting redundancy in the cancer cell's genetic program. Statement of Hypothesis: Activation of the RAS-MAPK pathway and/or dysregulation of the PI3Kinase pathway stimulate increased glucose uptake and a cascade of metabolic changes in glioblastoma cells that sustain high proliferative rates and support extensive cellular infiltration/migration in a heterogeneous tumor microenvironment. Aim 1: To define the metabolic phenotype of glioblastoma in a novel human orthotopic mouse model by 13C NMR spectral analysis of tumors following infusion of [U-13C]glucose or [1,2-13C]glucose to assess, respectively, the pathways intersecting in the citric acid cycle and relative flux through the pentose phosphate pathway. Aim 2: To determine the impact of Ras-MAPK pathway activation by EGFR overexpression and PI3K pathway dysregulation by deletion of PTEN, on the metabolic phenotype in genetically engineered glioblastoma mouse models. Aim 3: To determine whether modulation of IDH1 in the murine models of glioblastoma alters the flux through the citric acid cycle or pentose phosphate pathway. Aim 4: To correlate findings in Aims 1-3 with metabolic studies in patients with glioblastoma.