GENOTOXICITY OF DNA-DIRECTED ANTINEOPLASTIC AGENTS

许多用于治疗人类癌症的药物都会破坏dna。 药物，大多数这类药物具有诱变活性。很可能是 这种诱变潜力导致了一些不利的影响 化疗，如耐药的发生和发展 长期存活者的第二种癌症。这项研究的目的 在这里提出了对分子机制的理解。 某些化疗药物的致突变作用，需特别注意 对重要的诱变病变进行鉴定。这样的一种 了解这一点将有助于发展和选择 潜在的较少的诱变性和致癌剂。研究首先会 以新卡西汀和博莱霉素为中心的药物，其性质 DNA损伤及其序列特异性已被很好地描述。一个 将使用基于噬菌体lambda的ci基因的细菌系统 为了检验工作假设，对于这两种代理，修改了 含有氧化糖部分的无嘧啶中心是重要的 致突变的损伤。具体的问题包括(1)比较 脱嘧啶碱基突变的序列特异性 形成，(Ii)操纵无嘧啶中心的出现 在受控条件下处理完整的Lambda噬菌体或Lambda DNA 以及(Iii)检测DNA修复缺陷对突变的影响。 还将进行一些首字母缩写尝试，以检查其他 化疗药物。特别是，氮素芥菜是 致突变的双官能团烷基化试剂疑似引起高 第二种癌症的发病率。如果有足够强的诱变剂 反应可以在lambda ci基因中获得，频谱向前 将确定诱导的突变，作为阐明 这些诱变剂的分子诱变机制，关于这方面的研究很少 目前已知的。如果CI系统不够敏感，则会 另一种系统，基于插入到细菌中的抑制tRNA基因 质粒，将被开发出来。如果tRNA基因被证明是可行的 诱变探针，使其适用于哺乳动物研究的可能性 将探索细胞，首先检查其在 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.