OPTIMIZING TUMOR CYTOTOXICITY AFTER AGT INACTIVATION

AGT 失活后优化肿瘤细胞毒性

• 批准号: 6102784
• 负责人: STANTON L. GERSON
• 金额: $ 9.81万
• 依托单位: PENNSYLVANIA STATE UNIV HERSHEY MED CTR
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-09-30 至 1999-09-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6102784
• 关键词: CHO cells; DNA methylation; DNA repair; MCF7 cell; adduct; alkylating agents; alkyltransferase; antineoplastics; athymic mouse; carmustine; cytotoxicity; dosage; drug resistance; enzyme activity; enzyme inhibitors; guanine analog; immunocytochemistry; messenger RNA; monoclonal antibody; mutant; myeloid stem cell; pharmacokinetics; transfection; western blottings

Initial success utilizing O6-benzylguanine (BG) to inhibit O6-alkylguanine DNA alkyltransferase (AGT) provided proof in principal that AGT plays a major role in BCNU resistance in human tumors and that BG inactivation can markedly potentiate the effect of BCNU against these tumors in xenograft models. The hypothesis to be tested is that optimizing AGT inactivation will significantly improve the therapeutic response of agents which form cytotoxic O6-alkylguanine DNA adducts. First, simple inhibition of AGT is insufficient to maximize efficacy: most AGT+ tumors remain more resistant to BCNU than AGT-tumors. Superinhibitory doses of BG will be used with DNA methylation to maximize BCNU cytotoxicity. Secondly, a breast cancer cell line with acquired resistance to BG/BCNU has recently been identified, suggesting that resistance mechanisms will limit the efficacy of BG. The investigators will identify these mechanisms and develop strategies to overcome them. Third, tumors vary greatly in AGT and in the level of MGMT mRNA which affects the rate of AGT synthesis. How these influence the level of BCNU resistance has not been evaluated in vivo. Colon and breast tumor xenograft tumor models which mimic this diversity through either high AGT expression or BG resistance will be used as models of in vivo tumors which may be difficult to treat with BG/BCNU. These treatment refractory tumors will be exposed to newer BG-derivatives and with modified dose strategies to maximize biochemical modulation of resistance. Finally, BG/BCNU is toxic to normal tissues, particularly the marrow. A recently identified mutant AGT completely resistant to BG will be studied using gene transfer into marrow progenitors to provide selective marrow protection against combinations of BG for BG derivatives] & BCNU. Selective marrow protection may enhance potential clinical applications of AGT depletion. These studies are designed to enhance the utility of BG and derivative compounds as AGT inhibitors to overcome tumor resistance to this class of alkylating agents.

利用 O6-苄基鸟嘌呤 (BG) 抑制 O6-烷基鸟嘌呤初步成功 DNA 烷基转移酶 (AGT) 原则上证明 AGT 发挥着重要作用 BCNU 耐药性在人类肿瘤中起重要作用，BG 失活可以 显着增强 BCNU 对异种移植肿瘤的作用 模型。 要测试的假设是优化 AGT 失活 将显着改善药物的治疗反应，形成 细胞毒性 O6-烷基鸟嘌呤 DNA 加合物。 首先，简单地抑制AGT是 不足以最大限度地发挥功效：大多数 AGT+ 肿瘤仍然具有更强的耐药性 BCNU 比 AGT 肿瘤。 超抑制剂量的 BG 将与 DNA 一起使用 甲基化以最大化 BCNU 细胞毒性。 其次，乳腺癌细胞 最近发现了与 BG/BCNU 获得性耐药性相关的线， 表明耐药机制将限制 BG 的功效。 这 研究人员将确定这些机制并制定策略 克服他们。 第三，肿瘤的AGT和MGMT水平差异很大 影响 AGT 合成速率的 mRNA。 这些如何影响 BCNU 耐药水平尚未在体内进行评估。 结肠和乳房 肿瘤异种移植肿瘤模型通过高或低模拟这种多样性 AGT表达或BG抗性将用作体内肿瘤模型 BG/BCNU 可能难以治疗。 这些治疗难治 肿瘤将接触更新的 BG 衍生物并调整剂量 最大化耐药性生化调节的策略。 最后， BG/BCNU 对正常组织，特别是骨髓有毒。 最近一个 鉴定出的 AGT 完全抵抗 BG 的突变体将使用基因进行研究 转移到骨髓祖细胞中以提供选择性骨髓保护 与 BG 衍生物的 BG 组合] 和 BCNU 相比。 选择性骨髓 保护可能会增强 AGT 消耗的潜在临床应用。 这些研究旨在增强 BG 及其衍生物的效用 化合物作为 AGT 抑制剂来克服肿瘤对此类药物的耐药性 烷化剂。