FOLYLPOLYGLUTAMATE SYNTHETASE IN CANCER CHEMOTHERAPY

描述：(申请者摘要)该计划的长期目标是 通过利用叶基(或)的某些方面改善人类癌症的治疗 反叶-)聚谷氨酸合成。叶基多谷氨酸盐是细胞所必需的 生长，而经典的抗叶酸的多谷氨酸与其 细胞毒作用和耐药性，并可能在选择性方面发挥作用。详细 了解(抗)叶基多谷氨酸盐的合成和功能可能 从而允许设计新的代理或策略来利用这一关键过程。 这一长期目标将通过三个具体目标来实现：1. 叶基多谷氨酸合成酶的研究进展 多聚谷氨酸的合成，作为药物靶点。突变失活的FPGS是 因此，FPGS是一个潜在的癌症化疗靶点。缓蚀剂设计 是基于申请人使用的酶机制和结构-活性数据 重组人FPGS。经过专家叶酸化学家的合成 合作实验室，抗叶酸将在申请人的 实验室。最感兴趣的将是基于机制的优化 在上一次赠款期间发现的含磷缓蚀剂。类比 在完整细胞中既抑制纯化的FPGS又抑制多谷氨酰化(即， 将被研究以阐明它们的特异性和细胞性 效果。有希望的药物将接受初步毒性和疗效测试 以确定FPGS是否是一个有用的治疗靶点。2.确定 表观物理化学差异的功能意义 线粒体(MFPGS)和胞质(CFPGS)。虽然只有一个基因编码， MFPGS和cFPGS在SDS-PAGE迁移率上不同，这可能反映了功能 差异，特别是与抗叶酸抵抗力有关(目标3)。这个 申请者将探索这样的假设，即这种物理化学差异， 在这项资助下发现的，反映在动力学，底物特异性， 和/或法规变更。此外，由于结构性差异可能是 作为对功能的反思，他将检验由以下原因引起的假设 线粒体前导序列截短或翻译后修饰。 3.阐明cFPGS和mFPGS在MTX抗性中的作用。临床上，甲氨蝶呤是 通常是大剂量的片剂或短时间(24小时)输液。申请人 已经表明，这种疗法是通过缺乏FPGS来选择抗性的。FPGS是 在胞浆和线粒体中均有表达。MTX不能进入线粒体， 而减少的叶酸单谷氨酸盐可以。这是已知的(Shane等人)。那 MFPGS的单独表达可以在两者中建立叶基多谷氨酸池 胞浆和线粒体，并允许正常的细胞生长。因此，他假设 Cfpg的差异性下降，而不是两者的平行下降 亚型，可有助于抵抗脉冲MTX暴露。这也许可以解释 为什么在没有大电流的情况下会出现对脉冲MTX的高水平阻力 总的FPGS活性下降或谷氨酰水解酶活性上升。

DESCRIPTION: (Applicant's Abstract) The long-term goal of this program is to improve treatment of human cancer by exploiting aspects of folyl- (or antifolyl-) polyglutamate synthesis. Folylpolyglutamates are essential for cell growth, while polyglutamates of classical antifolates are implicated in their cytotoxic action and resistance and may have a role in selectivity. Detailed understanding of the synthesis and function of (anti)folylpolyglutamates may thus allow design of new agents or strategies to exploit this critical process. This long-term goal will be addressed through three specific aims: 1. Exploration of folylpolyglutamate synthetase (FPGS), the enzyme responsible for polyglutamate synthesis, as a drug target. Mutational inactivation of FPGS is lethal, thus FPGS is a potential cancer chemotherapy target. Inhibitor design is based on enzyme mechanism and structure-activity data of the applicant using recombinant human FPGS. After synthesis by expert folate chemists in collaborating laboratories, antifolates will be studied in the applicant's laboratory. Of primary interest will be the optimization of mechanism-based phosphorous-containing inhibitors found during the last grant period. Analogs that inhibit both purified FPGS and polyglutamylation in intact cells (i.e., are transported) will be studied to clarify their specificity and cellular effects. Promising drugs will undergo initial toxicity and therapeutic testing in vivo to define whether FPGS is a useful therapeutic target. 2. Determine the functional significance of the apparent physico-chemical difference between mitochondrial (mFPGS) and cytosolic FPGS (cFPGS). Although encoded by one gene, mFPGS and cFPGS differ in SDS-PAGE mobility, which may reflect a functional difference, particularly as related to antifolate resistance (Aim 3). The applicant will explore the hypothesis that this physico-chemical variance, discovered under this grant, is reflected in kinetic, substrate specificity, and/or regulation alterations. Also, since the structural difference may be reflective of function, he will examine hypotheses that it is caused by mitochondrial leader sequence truncation or by post-translational modification. 3. Elucidate the role of cFPGS and mFPGS in MTX resistance. Clinically, MTX is often given as a bolus or short (24 hr) infusion at high dose. The applicant has shown that this regimen selects for resistance via FPGS deficiency. FPGS is expressed in both cytosol and mitochondria. MTX cannot enter mitochondria, while reduced folate monoglutamates can. It is known (Shane et al.) that expression of mFPGS alone can establish folylpolyglutamate pools in both cytosol and mitochondria and allow normal cell growth. Thus, he hypothesizes that a differential decrease in cFPGS, rather than a parallel decrease in both isoforms, can contribute to resistance to pulse MTX exposure. This may explain why high-level resistance to pulse MTX can occur in the absence of a large decrease in total FPGS activity or a rise in glutamyl hydrolase activity.