FDH: A Novel Determinant of Tumor Suppression

FDH：肿瘤抑制的新决定因素

• 批准号: 8240898
• 负责人: SERGEY A KRUPENKO
• 金额: $ 24.84万
• 依托单位: MEDICAL UNIVERSITY OF SOUTH CAROLINA
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-03-01 至 2015-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8240898
• 关键词: Address; Anabolism; Apoptosis; Apoptotic; Award; Behavior; Binding; Biochemical Reaction; Budgets; Cancer Biology; Cancer cell line; Carbon; Cell Death; Cell Survival; Cell physiology; Cells; Complex; Cytoplasm; DHFR gene; DNA; DNA Repair; Diagnostic; Diet; Direct Costs; Disease; Down-Regulation; Enzyme Inhibitor Drugs; Enzyme Inhibitors; Enzymes; Epidemiologic Studies; Equilibrium; Evaluation; Folate; Folic Acid Deficiency; Formyltetrahydrofolates; Funding; Genes; Goals; Grant; Growth; Human; Hypermethylation; Investigation; Kidney; Knock-out; Licensing; Link; Liver; MAPK8 gene; MAPK9 gene; Mails; Malignant - descriptor; Malignant Neoplasms; Metabolic; Metabolic Pathway; Metabolism; Methylation; Molecular; NADP; Names; National Cancer Institute; Normal Cell; Nucleotide Biosynthesis; Onset of illness; Oxidoreductase; Pathway interactions; Phosphorylation; Physiological; Preventive; Process; Protein p53; Proteins; Publishing; Purines; RNA biosynthesis; Reaction; Regulation; Resistance; Role; Signal Transduction; Specialist; Stream; Stress; Supplementation; Susceptibility Gene; Targeted Research; Telefacsimile; Testing; Tetrahydrofolates; Text; Thinking; Transcriptional Activation; Tumor Suppression; Tumor Suppressor Proteins; Tumor Tissue; United States National Institutes of Health; Visit; base; cancer cell; carcinogenesis; cell motility; cytotoxicity; design; folic acid metabolism; in vivo; insight; mouse model; mutant; neoplastic cell; novel; payment; preference; promoter; purine; research study; tumor; tumor initiation; tumorigenesis; tumorigenic

DESCRIPTION (provided by applicant): The overall goal of this proposal is to characterize the novel tumor suppressor activity of a key metabolic enzyme and determine the mechanisms transforming metabolic effects into regulation of proliferation. FDH (10-formyltetrahydrofolate dehydrogenase) irreversibly converts 10-formyltetrahydrofolate, an essential substrate for de novo purine biosynthesis, to tetrahydrofolate. Through depletion of this substrate, FDH can restrict purine biosynthesis. In turn, this interferes with important downstream cellular processes, including DNA/RNA biosynthesis and DNA repair. Because of this critical metabolic function, down-regulation of FDH in cancer cells was predicted to be pro-survival. Indeed, we have initially made the important observation that FDH is strongly and ubiquitously down-regulated in tumors through the promoter hypermethylation. We have further demonstrated that moderate FDH expression in FDH-deficient cancer cells induces apoptotic cell death. In contrast, non-cancer cells are insensitive to high levels of the enzyme. Therefore, it is proposed that cancer cells silence the FDH gene in order to escape cytotoxicity. Studies of phenotypic effects upon reactivation of normal FDH expression in FDH-deficient tumor cells have further explored JNK1/2 and p53 as key components of FDH-induced apoptotic signaling, and determined DHFR and folate supplementation as proliferation rescue factors. Importantly, a novel pathway linking FDH, through intracellular folate regulation, to control of cell motility, was discovered. The current proposal extends previous studies of antiproliferative mechanisms of FDH, and related folates, to direct interaction with p53, their role in motility and possibly metastasis, and evaluation of its role in vivo in mouse model. Our central hypothesis is that FDH down- regulation through promoter hypermethylation is one of the important means by which malignancies gain pro- survival advantage over normal cells. We further suggest that FDH exerts its regulatory effects through multiple mechanisms. The Specific Aims to probe these mechanisms and test our hypothesis are: (1) Investigate the functional interaction of FDH with p53 tumor suppressor protein in cytoplasm. (2) Elucidate the molecular mechanisms leading to inhibition of cell motility by folate stress. (3) Determine the impact of FDH silencing on tumor initiation/progression using FDH deficient mouse model. Investigation of the critical role of FDH, in cancer cell survival/induction of folate stress at the onset of the disease, will provide important insight into the malignant process itself and link deregulation of key metabolic pathways to cancer disease, as well as establish new targets for diagnostics of the malignant transformation. PUBLIC HEALTH RELEVANCE: Folate, an important and essential part of the human diet, regulates many cellular processes including nucleotide biosynthesis and methylation, while folate deficiency promotes many diseases. This application is focused on a novel tumor suppressor function of FDH, an abundant human enzyme, which is an important regulator of folate pathways. Since FDH can function as a restrictor of excessive proliferation, understanding its role in cellular metabolism will provide better understanding of tumorigenic processes.

描述（由申请人提供）：本提案的总体目标是表征关键代谢酶的新型肿瘤抑制活性，并确定将代谢效应转化为增殖调节的机制。FDH（10-甲酰四氢叶酸脱氢酶）不可逆地将10-甲酰四氢叶酸（嘌呤从头生物合成的必需底物）转化为四氢叶酸。通过消耗这种底物，FDH可以限制嘌呤的生物合成。反过来，这会干扰重要的下游细胞过程，包括DNA/RNA生物合成和DNA修复。由于这种关键的代谢功能，预测癌细胞中FDH的下调有利于存活。事实上，我们已经初步做出了重要的观察，即FDH通过启动子超甲基化在肿瘤中强烈且普遍地下调。我们已经进一步证明，在FDH缺陷的癌细胞中适度的FDH表达诱导凋亡性细胞死亡。相反，非癌细胞对高水平的酶不敏感。因此，提出癌细胞沉默FDH基因以逃避细胞毒性。在FDH缺陷肿瘤细胞中正常FDH表达再激活后的表型效应的研究进一步探索了JNK 1/2和p53作为FDH诱导的凋亡信号传导的关键组分，并确定DHFR和叶酸补充作为增殖拯救因子。重要的是，发现了一种通过细胞内叶酸调节将FDH连接到细胞运动控制的新途径。目前的建议扩展了以前的FDH和相关叶酸的抗增殖机制的研究，直接与p53的相互作用，其在运动和可能的转移中的作用，并在小鼠模型中评价其在体内的作用。我们的中心假设是，通过启动子超甲基化的FDH下调是恶性肿瘤获得比正常细胞更高的生存优势的重要手段之一。我们进一步认为，FDH通过多种机制发挥其调节作用。本研究的具体目的是：（1）研究FDH与p53抑癌蛋白在胞浆中的相互作用。(2)阐明叶酸胁迫抑制细胞运动的分子机制。(3)使用FDH缺陷型小鼠模型确定FDH沉默对肿瘤起始/进展的影响。调查FDH在癌症发病时癌细胞存活/诱导叶酸应激中的关键作用，将为恶性过程本身提供重要的见解，并将关键代谢途径的失调与癌症疾病联系起来，以及建立诊断恶性转化的新靶点。 公共卫生关系：叶酸是人类饮食的重要组成部分，调节许多细胞过程，包括核苷酸生物合成和甲基化，而叶酸缺乏会促进许多疾病。本申请集中于FDH的新的肿瘤抑制功能，FDH是一种丰富的人类酶，其是叶酸途径的重要调节剂。由于FDH可以作为过度增殖的限制器，了解其在细胞代谢中的作用将提供更好地了解肿瘤发生过程。