GENOTOXICITY OF ANTINEOPLASTIC DNA-CLEAVING AGENTS

描述：几种癌症化疗药物，包括 拟放射性药物和拓扑异构酶抑制剂诱导特定类型的 末端阻断的DNA双链断裂，这些病变 涉及细胞毒性和致突变作用， 化合物. 此外，拟放射性化合物，如电离 辐射本身，诱导一小部分的全球基因组不稳定性， 处理过的细胞的后代。 建议的第一个主要目标 研究是为了确定一个明显的严格性和性质 特异性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 不稳定性，如通过染色体重排以及其他 标准，将定量评估各类突变体 在CHO细胞中通过拟放射性试剂博来霉素和 新制癌素和拓扑异构酶II抑制剂安吖啶。 的 研究的第二个主要目标是确定 DNA-PK在这三种诱导的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 在加强修复的保真度方面。 为此，突变诱导 通过博来霉素在缺乏这种激酶的CHO细胞亚系中的作用， 与亲本CHO细胞中产生的现有突变体相比， 这显然是由于双链末端连接不准确而引起的 休息. 通过末端连接的修复也将在体外进行检查，使用 基于非洲爪蟾卵提取物和合成基质的系统， 定义，化学修饰的DNA末端，再次强调定义 DNA-PK在末端连接过程中的生物化学作用， 因为它涉及到修复保真度。 两者之间的关系-- 链断裂修复、修复保真度和获得性基因组不稳定性 应该对正常的整体反应有重要的影响， 和肿瘤细胞的双链裂解剂，并可能在长期 术语有助于操纵细胞反应， 降低这些药物的致癌性。

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.