SIGNIFICANCE OF GGT EXPRESSION IN TUMORS

GGT 表达在肿瘤中的意义

• 批准号: 2712658
• 负责人: MARIE H HANIGAN
• 金额: $ 20.28万
• 依托单位: UNIVERSITY OF VIRGINIA
• 依托单位国家: 美国
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-08-01 至 1999-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2712658
• 关键词: 3T3 cells; athymic mouse; cis platinum compound; drug metabolism; drug resistance; enzyme activity; enzyme induction /repression; enzyme mechanism; gene expression; kidney cell; laboratory rat; mass spectrometry; molecular oncology; neoplasm /cancer chemotherapy; neoplastic cell; nonhuman therapy evaluation; ovary neoplasms; protein glutamine gamma glutamyltransferase; renal toxin; renal tubule; transfection

Studies accomplished during the initial funding period of this grant have led to the discovery of a new in vivo pathway of cisplatin metabolism, Cisplatin, one of the most commmonly used drugs in the treatment of human tumors, is nephrotoxic. The new evidence reveals that rats produce a circulating metabolite of cisplatin that is activated to a potent nephrotoxin by the enzyme gamma-glutamyl transpeptidase (GGT), located on the luminal surface of the proximal tubule cells. The therapeutic effect of cisplatin is attribute to its ability to kill dividing cell by damaging DNA. However, the types of tumors that respond to cisplatin contain GGT- positive cells. The GGT-dependent mechanism responsible for acute nephrotoxicity may be the dominant mechanism by which cisplatin kills tumor cells. The goal of the studies proposed in this renewal application is to determine whether the GGT-dependent pathway of cisplatin metabolism is a major component of the therapeutic effect of cisplatin. Three specific aims are proposed: First, the nephrotoxic metabolite of cisplatin will be isolated, purified and identified. A novel in vitro assay system that identify compounds which are converted to biologically active toxins by GGT will be used to monitor the isolation of the nephrotoxic metabolite. Second, experiments are proposed to test whether GGT-positive tumors are more sensitive than GGT-negative tumors to the in vivo toxicity of cisplatin. In brief, this will be done transfecting GGT into two human tumor cell lines, injecting the cells into nude mice, treating the resulting tumors with cisplatin and assessing the response of the GGT- positive and GGT-negative tumors. Third, methods for inducing GGT expression in human epithelial ovarian tumors will be studied. Ovarian tumor which initially respond to cisplatin then develop resistance, are a mixture of GGT-positive and GGT-negative cells. The resistant tumor may be the result of an outgrowth of GGT-negative cells. Preliminary studies establish that several chemotherapeutic agents induce GGT expression in human ovarian tumor cell in vitro. These new results could lead to chemotherapeutic protocols that sensitize tumors to cisplatin and profoundly increase the number of tumors that can be cured. Introduction of cisplatin into clinical use increased the cure rate for testicular tumors, which are strongly GGT-positive, from less than 20% to greater than 90%. Other tumors show initial response to cisplatin, but become resistant. The research out lined in this proposal will offer important new insights on cisplatin metabolism and may define combination chemotherapy protocols that will restore the initial promise of cisplatin as a cure for many human tumors.

在这笔赠款的初始资助期内完成的研究 导致了顺铂体内代谢的新途径的发现， 顺铂是治疗人类癌症最常用的药物之一 肿瘤是肾毒性的。新的证据表明，老鼠会产生一种 顺铂的循环代谢物被激活为有效的 肾毒素是由γ-谷氨酰转肽酶(GGT)引起的，位于 近端小管细胞的管腔表面。治疗效果观察 顺铂的作用归因于其通过破坏 DNA然而，对顺铂有反应的肿瘤类型含有GGT- 阳性细胞。急性心肌梗死的GGT依赖机制 肾毒性可能是顺铂致死的主要机制 肿瘤细胞。在此续期申请中提出的研究目标 目的是确定依赖GGT的顺铂代谢途径 是顺铂疗效的主要组成部分。三 提出了具体目标：第一，顺铂的肾毒性代谢物 将被分离、提纯和鉴定。一种新型的体外检测系统 识别被转化为生物活性毒素的化合物 将GGT用于监测肾毒素的分离 代谢物。其次，提出了检测GGT阳性的实验。 肿瘤比GGT阴性肿瘤对体内毒性更敏感 顺铂。简而言之，这将通过将GGT导入两个人体内而完成 肿瘤细胞系，将细胞注射到裸鼠体内，治疗 顺铂引起的肿瘤并评估GGT的疗效 GGT阳性和GGT阴性肿瘤。第三，诱发GGT的方法 我们将研究其在人卵巢上皮性肿瘤中的表达。卵巢 最初对顺铂有反应然后产生耐药性的肿瘤是一种 GGT阳性细胞和GGT阴性细胞的混合物。耐药肿瘤可能是 这是GGT阴性细胞生长的结果。初步研究 几种化疗药物诱导细胞GGT表达的实验研究 体外培养人卵巢肿瘤细胞。这些新的结果可能会导致 化疗方案使肿瘤对顺铂和 大大增加了可以治愈的肿瘤数量。引言 顺铂投入临床应用提高睾丸治愈率 GGT强阳性的肿瘤，从不到20%到更大 而不是90%。其他肿瘤对顺铂表现出初步反应，但 抵抗力强。这项提案中列出的研究将提供重要的 对顺铂代谢的新见解，并可能定义联合 将恢复顺铂最初希望的化疗方案 作为治疗许多人类肿瘤的良药。