FDH: A Novel Determinant of Tumor Suppression

这项提议的总体目标是表征新的肿瘤抑制活性 一种关键的代谢酶，并确定代谢效应的转化机制 对扩散的调控。10-甲酰基四氢叶酸脱氢酶 不可逆地转化10-甲酰基四氢叶酸，这是从头合成嘌呤的基本底物 生物合成，到四氢叶酸。通过消耗这种底物，外佣可以限制 嘌呤生物合成。这会干扰DNA/RNA的生物合成和DNA修复。 由于这一关键的代谢功能，癌细胞中FDH的下调将 支持生存。事实上，我们初步观察到，外佣是 通过启动子在肿瘤中强烈且普遍下调 高甲基化。我们进一步证明FDH的适度表达在 FDH缺陷的癌细胞可诱导细胞凋亡。相比之下，非癌细胞 对高水平的酶不敏感。因此，有人提出，癌细胞 沉默FDH基因以逃避细胞毒性。表型效应的研究 FDH缺陷肿瘤细胞中正常FDH表达的重新激活进一步 探讨了JNK1/2和P53作为FDH诱导的细胞凋亡信号的关键成分，以及 确定补充DHFR和叶酸为细胞增殖的挽救因素。 重要的是，一种新的途径通过细胞内叶酸调节将外佣连接到 发现了对细胞运动的控制。目前的提案扩展了之前的研究 FDH及其相关叶酸直接与P53相互作用的抗增殖机制 并对其在小鼠体内的作用进行评价。我们的中心假设是外佣 通过启动子超甲基化下调是一种重要手段 与正常细胞相比，哪些恶性肿瘤获得了有利于生存的优势。我们进一步建议 外佣通过多种机制发挥其监管作用。具体目的是 探讨这些机制并验证我们的假设是：(1)研究功能 FDH与P53抑癌蛋白在胞浆内的相互作用(2)确定 FDH沉默对FDH基因缺陷小鼠肿瘤发生和发展的影响 模特。FDH在癌细胞存活/叶酸诱导中的关键作用研究 在疾病开始时的压力，将提供对恶性的重要洞察 过程本身，并将关键代谢途径的放松与癌症疾病联系起来 为恶性转化的诊断建立新的靶点。

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. This interferes with DNA/RNA biosynthesis and DNA repair. Because of this critical metabolic function, down-regulation of FDH in cancer cells would 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 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) 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.