Role of Glutaminolysis in the Myc-induced Metabolic Phenotype of Tumor Cells

描述（由申请人提供）：葡萄糖和谷氨酰胺代谢的重编程是恶性转化的关键事件。然而，这些适应背后的功能驱动因素和分子途径现在才刚刚开始出现。我们的长期目标是了解肿瘤细胞代谢重编程的机制，以便分子癌症治疗能够针对这些过程。本申请的总体目标是应用系统方法来阐明 Myc 癌蛋白过度表达引起的谷氨酰胺分解表型的功能作用。 Myc 是肿瘤细胞中有氧糖酵解和谷氨酰胺分解的重要调节剂，后者的特点是大量消耗非必需氨基酸谷氨酰胺。我们的中心假设是，Myc 过度表达诱导的谷氨酰胺分解表型对于对抗氧化应激和促进快速分裂细胞中的脂质合成非常重要。这项研究的基本原理是，一旦我们确定了 Myc 诱导的代谢重编程的功能意义，这些过程就可以有针对性地破坏它们赋予肿瘤细胞的优势。我们计划通过追求以下具体目标来检验我们的中心假设：（1）确定谷氨酰胺分解在活性氧解毒中的作用；（2）确定谷氨酰胺分解在促进脂质合成中的作用。拟议的研究具有创新性，因为它应用系统方法来定量阐明综合代谢网络的全局行为，而不是孤立的单个反应或节点。我们将应用代谢流分析 (MFA) 来量化 P493-6 Burkitt 淋巴瘤细胞以及依赖 Myc 进行恶性转化的小鼠胚胎成纤维细胞的代谢表型。这些细胞含有 Myc 构建体，可以对其进行调节以实现调整的过度表达水平。这些细胞将接受不同的处理，旨在阐明糖酵解和谷氨酰胺分解在细胞氧化还原平衡和回补过程中的作用。特别是，我们将同时量化胞质 NADPH 产生的所有三种主要途径的通量，这对于维持增殖细胞中的氧化还原稳态非常重要。此外，我们将研究将葡萄糖和谷氨酰胺转化为支持细胞生长所需的脂质中间体的途径的调节。通过这项工作，我们希望能够更深入地了解 Myc 如何调节细胞代谢以及这些适应如何为肿瘤细胞提供生长优势。这很重要，因为它将刺激寻找能够抑制 Myc 依赖性肿瘤进展的新药物靶点。这项工作还将通过识别 Myc 过度表达的独特代谢特征，为个性化医疗提供一条途径。

DESCRIPTION (provided by applicant): Reprogramming of glucose and glutamine metabolism is a key event in malignant transformation. However, the functional drivers and molecular pathways underlying these adaptations are only now starting to emerge. Our long-term goal is to understand mechanisms of metabolic reprogramming in tumor cells so that these processes can be targeted by molecular cancer therapeutics. The overall objective of the current application is to apply systems approaches to elucidate the functional role of the glutaminolytic phenotype elicited by overexpression of the Myc oncoprotein. Myc is an important regulator of both aerobic glycolysis as well as glutaminolysis in tumor cells, the latter of which is characterized by avid consumption of the non-essential amino acid glutamine. Our central hypothesis is that the glutaminolytic phenotype induced by Myc overexpression is important for combating oxidative stress and fueling lipid synthesis in rapidly dividing cells. The rationale for the proposed research is that, once we have identified the functional significance of Myc- induced metabolic reprogramming, these processes can be targeted to undermine the advantages they confer on tumor cells. We plan to test our central hypothesis by pursuing the following specific aims: (1) to determine the role of glutaminolysis in detoxification of reactive oxygen species and (2) to determine the role of glutaminolysis in promoting lipid synthesis. The proposed research is innovative because it applies systems approaches to quantitatively elucidate the global behavior of integrated metabolic networks, rather than individual reactions or nodes in isolation. We will apply metabolic flux analysis (MFA) to quantify metabolic phenotypes in P493-6 Burkitt's lymphoma cells as well as mouse embryonic fibroblasts that are dependent on Myc for their malignant transformation. These cells contain Myc constructs that can be modulated to achieve tuned levels of overexpression. The cells will be subjected to different treatments intended to elucidate the role of glycolysis and glutaminolysis in both cellular redox balancing and anaplerotic processes. In particular, we will simultaneously quantify flux through all three major routes of cytosolic NADPH production, which are important for maintenance of redox homeostasis in proliferating cells. Furthermore, we will investigate the regulation of pathways that serve to convert glucose and glutamine into lipid intermediates required to support cell growth. As a result of this work, we expect to contribute a deeper understanding of how Myc regulates cellular metabolism and how these adaptations provide a growth advantage to tumor cells. This is significant because it will stimulate the search for novel drug targets that can inhibit the progression of Myc-dependent tumors. This work will also provide an avenue toward personalized medicine by identifying the unique metabolic signatures of Myc overexpression.