GENOTOXICITY OF ANTINEOPLASTIC DNA-CLEAVING AGENTS

描述：几种癌症化疗药物，包括 拟放射药物和拓扑异构酶抑制剂诱导特定类型 末端受阻的DNA双链断裂，这些损伤 与这些病毒的细胞毒性和致突变作用有关 化合物。此外，拟辐射化合物，如电离 辐射本身，在一小部分中导致全球基因组不稳定 经过处理的细胞的后代。提出的第一个主要目标 研究就是要确定严格性和表面性 特定的双链断裂错误修复事件与 获得基因组不稳定性。为此，基因组学 不稳定性，由染色体重排和其他 标准，将在不同类别的突变体中进行定量评估 拟辐射药物博莱霉素和博莱霉素对CHO细胞的诱导 新卡宾抑素，以及拓扑异构酶II抑制剂阿马西林。这个 研究的第二个主要目标是确定可能的作用 DNA-PK在三者所致双链断裂修复中的作用 药物，特别强调DNA-PK是否发挥积极作用 在执行修复的保真度方面。为此，突变导致 用博莱霉素诱导的CHO细胞亚系中缺乏该激酶的亚系将 与亲本CHO细胞中产生的现有突变体相比，突变体 这显然是由于双链末端连接不准确引起的 休息一下。通过末端连接修复也将在体外进行检测，使用 基于非洲爪哇卵提取液和合成底物的系统 定义的、化学修饰的DNA末端，同样强调定义 DNA-PK在末端连接过程中的生化作用 因为它与修复保真度有关。双重奏之间的关系 链断裂修复、修复保真度和获得性基因组不稳定性 应该对正常的总体反应有重要的影响 和肿瘤细胞的双链裂解剂，并可能在长时间内 在努力操纵细胞反应以增加 这些药剂的功效和降低致癌性。

DESCRIPTION: Several cancer chemotherapeutic agents, including radiomimetic drugs and topoisomerase inhibitors induce specific types of terminally blocked DNA double-strand breaks, and these lesions have been implicated in both cytotoxic and mutagenic effects of these compounds. In addition, the radiomimetic compounds, like ionizing radiation itself, induce a global genomic instability in a fraction of the progeny of treated cells. The first major goal of the proposed studies is to determine the stringency and the nature of an apparent linkage between specific double-strand break misrepair events and the acquisition of genomic instability. Toward this end, genomic instability, as judged by chromosome rearrangements as well as other criteria, will be quantitatively assessed in various classes of mutants induced in CHO cells by the radiomimetic agents bleomycin and neocarzinostatin, and by the topoisomerase II inhibitor amsacrine. The second major goal of the studies is to determine the possible role of DNA-PK in the repair of double-strand breaks induced by these three agents, with particular emphasis on whether DNA-PK play an active role in enforcing the fidelity of the repair. To this end, mutations induced by bleomycin in CHO cell sublines deficient in this kinase will be compared to existing mutants generated in parental CHO cells, mutants which apparently arise by inaccurate end-joining of double-strand breaks. Repair by end-joining will also be examined in vitro, using a system based on Xenopus egg extracts and synthetic substrates bearing defined, chemically modified DNA ends, again with emphasis on defining the biochemical role of DNA-PK in the end-joining process, particularly as it relates to repair fidelity. The relationship between double- strand break repair, repair fidelity, and acquired genomic instability should have important implications for the overall response of normal and tumor cells to double-strand cleaving agents, and may in the long term aid in efforts to manipulate cellular responses so as to increase the efficacy and reduce the carcinogenicity of these agents.