COMBATING ALKYLATING AGENT RESISTANCE IN HUMAN GLIOMAS

描述（改编自研究者摘要）：恶性胶质瘤 预后极差，中位生存率低于2 年虽然最常见于老年人，这些恶性肿瘤是第三位的。 是15至34岁人群癌症死亡的主要原因。而且 恶性神经胶质瘤的发病率在65岁以上的人中增加。烷基化 药物，当用于单药或联合化疗沿着 手术和放射治疗是最有效的抗肿瘤药物 成人胶质瘤的然而，对烷基化的内在和获得性抗性 代理限制了它们的用途。广泛的长期目标是确定 DNA修复机制在胶质瘤化疗耐药中的作用 试剂（甲基化和氯乙基化试剂），并确定战略， 战斗阻力。申请人已经表明，9种人神经胶质瘤的抗性 细胞系对烷化剂的依赖性是基于除了 DNA修复蛋白O 6-甲基鸟嘌呤-DNA甲基转移酶（MGMT）。他们的 假设是3-甲基腺嘌呤-DNA糖基化酶（3-MAG），一种 启动N3-甲基腺嘌呤和其它N-烷基嘌呤的碱基切除修复， 也有助于抵抗。为了证实这一假设， 证明3-MAG的主要底物N3-甲基腺嘌呤是致死的 通过将加合物去除与对 MeOSO 2（CH 2）2-lexitropsin，最近开发的烷基化剂， 仅在腺嘌呤的N3原子上。他们还将使用反义mRNA 表达抑制3-MAG在以前分析的胶质瘤细胞系中，我们 具有定量的烷化剂细胞毒性和MGMT对 阻力他们将定量反义表达对3-MAG的影响， mRNA和酶水平，以及氯乙基化和甲基化试剂 不存在和存在O 6-苄基鸟嘌呤（底物）时的细胞毒性 MGMT的类似物抑制剂。在相关工作中，他们将一起定量3-MAG， 与MGMT，在新诊断和复发的脑肿瘤，并评估 酶水平与烷化剂治疗反应的关系。的 组织研究和体外研究将帮助他们识别 潜在有效的烷化剂/抑制剂疗法。如果他们的假设 是正确的，3-MAG的抑制剂最终可能会在临床上进行测试， 用O 6-苄基鸟嘌呤同时抑制或不同时抑制MGMT。这是一个 逻辑上的预期是，不同靶向抑制剂的组合 可能有效地加强烷化剂化疗的成人胶质瘤。 这是一份修改后的申请。该项目的长期目标是确定 DNA修复机制在胶质瘤烷化剂抗性中作用 化疗剂。概述了三个具体目标，以测试 假设3-甲基腺嘌呤DNA糖基化酶，启动碱基 N3-meAd和其他N-烷基嘌呤的切除修复有助于烷基化 代理人抵抗具体目标1将试图建立未修复的 N3-meAd DNA加合物对人脑胶质瘤细胞具有毒性。具体目标2将 确定3-MAG水平的调节是否影响对甲基化的敏感性 和氯乙基化剂。具体目标3将测量3-MAG的水平 和MGMT在新诊断和复发的脑肿瘤中的作用。为了定义 3-MAG的作用与临床耐药、酶水平的高低有关 对烷化剂辅助治疗和临床病程有反应。

DESCRIPTION (As Adapted From the Investigator's Abstract): Malignant gliomas have an extremely poor prognosis with median survival rates of less than 2 years. Although most frequent in older adults, these malignancies are the third leading cause of cancer deaths in persons 15 to 34 years of age. Moreover, the incidence of malignant gliomas is increasing in those older than 65. Alkylating agents, when used in single agent or combination chemotherapy along with surgery and radiation, are the most effective antitumor drugs for the treatment of adult gliomas. However, intrinsic and acquired resistance to alkylating agents limits their usefulness. The broad, long-term objective is to define the contribution of DNA repair mechanisms to glioma resistance to chemotherapeutic agents (methylating and chloroethylating agents), and to identify strategies to combat resistance. The applicants have shown that resistance of 9 human glioma cell lines to alkylating agents is based on a mechanism(s) in addition to the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT). Their hypothesis is that the 3-methyladenine-DNA glycosylase (3-MAG), an enzyme which initiates base excision repair of n3-methyladenine and other N-alkylpurines, also contributes to resistance. To confirm this hypothesis, they will demonstrate that N3-methyladenine, the principal substrate of 3-MAG, is lethal to human glioma cells by correlating adduct removal with sensitivity to MeOSO2(CH2)2-lexitropsin, a recently developed alkylator that methylates almost exclusively at the N3 atom of adenine. They will also use antisense mRNA expression to suppress 3-MAG in previously analyzed glioma lines in which we have quantitated alkylating agent cytotoxicity and the contribution of MGMT to resistance. They will quantitate the effect of antisense expression on 3-MAG mRNA and enzyme levels, and on chloroethylating and methylating agent cytotoxicity in the absence and presence of O6-benzylguanine, a substrate analog inhibitor of MGMT. In related work, they will quantitate 3-MAG, together with MGMT, in newly diagnosed and recurrent brain tumors, and asses the relationship of enzyme levels to response to alkylating agent therapy. The tissue studies, together with the in vitro work, will aid them in identifying potentially effective alkylating agent/inhibitor therapies. If their hypothesis is correct, inhibitors of 3-MAG might eventually be tested clinically, either with or without concurrent inhibition of MGMT with O6-benzylguanine. It is a logical expectation that a combination of differentially targeted inhibitors might effectively potentiate alkylating agent chemotherapy for adult gliomas. This is a revised application. The long-term goals of the project are to define the contribution of DNA repair mechanisms to glioma resistance to alkylating chemotherapeutic agents. Three specific aims are outlined to test the hypothesis that 3-methyladenine DNA glycosylase, the enzyme that initiates base excision repair at N3-meAd and other N-alkyl purines, contributes to alkylating agent resistance. Specific aim 1 will attempt to establish that unrepaired N3-meAd DNA adducts are toxic to human glioma cells. Specific aim 2 will determine whether modulation of 3-MAG levels affects sensitivity to methylating and chloroethylating agents. Specific aim 3 will measure the levels of 3-MAG and MGMT in newly diagnosed and recurrent brain tumors. In an effort to define the role of 3-MAG in clinical drug resistance, enzyme levels will be correlated with response to alkylator adjuvant therapy and clinical course.