COMBATING ALKYLATING AGENT RESISTANCE IN HUMAN GLIOMAS

描述(改编自《调查者摘要》)：恶性胶质瘤 预后极差，中位存活率低于2 好几年了。虽然最常见于老年人，但这些恶性肿瘤排在第三位。 15至34岁人群中癌症死亡的主要原因。此外， 在65岁以上的人群中，恶性胶质瘤的发病率正在上升。烷基化 药物在单剂或联合化疗中与 手术和放射治疗，都是最有效的抗肿瘤药物 成人神经胶质瘤。然而，对烷基化的固有和获得性抵抗 代理人限制了他们的用处。广泛而长期的目标是定义 DNA修复机制在脑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，以 战斗抵抗。申请者已经证明了9例人脑胶质瘤的耐药性 细胞系去烷化剂是基于一种机制(S)除了 DNA修复蛋白O6甲基鸟嘌呤DNA甲基转移酶(MGMT)。他们的 假说是3-甲基腺嘌呤-DNA糖基酶(3-MAG)，一种可以 启动n3-甲基腺嘌呤和其他N-烷基嘌呤的碱基切除修复， 也会导致抵抗。为了证实这一假设，他们将 证明3-MAG的主要底物N3-甲基腺嘌呤是致命的 通过将加合物去除与药物敏感性相关联来抑制人脑胶质瘤细胞 MeOSO2(CH2)2-lexitropsin，一种最近开发的烷化剂，几乎甲基化 只针对腺嘌呤的N3原子。他们还将使用反义mrna 在先前分析的胶质瘤细胞系中抑制3-MAG的表达 已经定量了烷化剂的细胞毒性和MGMT对 抵抗。他们将量化反义表达对3-MAG的影响 MRNA和酶水平，以及氯乙基化和甲基化试剂 底物O6-苄基鸟嘌呤存在和不存在时的细胞毒性 MGMT的模拟抑制剂。在相关工作中，他们将一起对3-MAG进行量化 在新诊断和复发的脑肿瘤中使用MGMT，并评估 酶水平与烷化剂治疗反应的关系。这个 组织研究和体外工作将帮助他们识别 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 同时或不同时抑制MGMT和O6-苄基鸟嘌呤。这是一个 合乎逻辑的预期是，不同靶向的抑制剂组合 可能有效加强烷化剂化疗对成人胶质瘤的治疗。 这是一份修改后的申请表。该项目的长期目标是定义 DNA修复机制在脑胶质瘤烷化耐药中的作用 化疗药物。概述了三个具体的目标来测试 假设3-甲基腺嘌呤DNA糖基酶，启动碱基的酶 N3-Mead和其他N-烷基嘌呤的切除修复有助于烷基化 抗药性。特定目标1将尝试建立未修复 N3-Mead DNA加合物对人胶质瘤细胞有毒性。特定目标2将 确定3-MAG水平的调节是否影响对甲基化的敏感性 和氯乙基化试剂。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。在努力定义 3-MAG在临床耐药中的作用与酶水平相关 对烷化剂辅助治疗有反应及临床病程。

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.