GENOTOXICITY OF DNA-DIRECTED ANTINEOPLASTIC AGENTS

许多用于治疗人类癌症的药物都是破坏DNA的 药剂，并且大多数此类药物具有诱变活性。 很可能 这种潜在的致突变性导致了 化疗，如耐药性的发生和发展， 长期存活者的第二种癌症。 研究的目的 这里提出的是一个理解的分子机制， 通过某些化学治疗剂的诱变，特别注意 鉴定重要的致突变病变。 这样的 理解将有助于发展和选择 潜在的致突变性和致癌性较低的物质。 研究将首先 新制癌素和博来霉素，药物的性质， DNA损伤及其序列特异性已得到很好的表征。 一 将使用基于λ噬菌体cI基因的细菌系统 为了验证工作假设，对于这两种药物， 含有氧化糖部分的无嘧啶位点是重要的 致突变损伤 具体方法将包括（1）比较 无嘧啶位点突变的序列特异性 形成，（ii）操纵无嘧啶位点的发生， 在受控条件下处理完整λ噬菌体或λ DNA 和（iii）检测DNA修复缺陷对诱变的影响。 还将进行一些初步尝试，以检查其他突变。 化疗剂。 特别地，氮化合物是 致突变双功能烷化剂，疑似引起高 第二种癌症的发病率。 如果足够强的诱变剂 响应可以在λ cI基因中获得，前向光谱 将确定诱导的突变，作为阐明突变的第一步， 诱变的分子机制，这些代理人，其中很少是 目前已知。 如果cI系统不够灵敏， 另一种系统，基于插入细菌中的抑制tRNA基因， 质粒，将被开发。 如果tRNA基因被证明是一种可行的 诱变探针，使其适应哺乳动物研究的可能性 细胞将被探索，首先检查其在一个 哺乳动物病毒载体。

Many of the drugs used in the treatment of human cancers are DNA-damaging agents, and most such drugs possess mutagenic activity. It is likely that this mutagenic potential contributes to some of the adverse effects of chemotherapy, such as the onset of drug resistance and the development of second cancers in long-term survivors. The objective of the research proposed here is an understanding of the molecular mechanisms of mutagenesis by certain chemotherapeutic agents, with particular attention to identification of the important mutagenic lesions. Such an understanding would be useful in the development and selection of potentially less mutagenic and carcinogenic agents. Studies will at first center on neocarzinostatin and bleomycin, agents for which the nature of DNA damage and its sequence specificity have been well characterized. A bacterial system based on the cI gene of bacteriophage lambda will be used to test the working hypothesis that, for both these agents, modified apyrimidinic sites containing oxidized sugar moieties are important mutagenic lesions. Specific aproaches will include (1) comparison of the sequence specificity of mutagenesis with that of apyrimidinic site formation, (ii) manipulation of the occurence of apyrimidinic sites by treatment of intact lambda phage or lambda DNA under controlled conditions and (iii) examination of the effects of DNA repair defects on mutagenesis. Some initials attempts will also be made to examine mutagenesis by other chemotherapeutic agents. In particular, the nitrogen mustards are mutagenic bifunctional alkylating agents suspected of causing a high incidence of second cancers. Provided that a sufficiently strong mutagenic response can be obtained in the lambda cI gene, the spectrum of forward mutations induced will be determined, as a first step in elucidation the molecular mechanisms of mutagenesis by these agents, about which little is presently known. If the cI system is not sufficiently sensitive, an alternative system, based on a suppressor tRNA gene inserted in a bacterial plasmid, will be developed. If the tRNA gene proves to be a workable mutagenesis probe, the possibility of adapting it to studies in mammalian cells will be explored, beginning with examination of its stability in a mammalian viral vector.