DNA REPAIR AND ANTITOPOISOMERASE DRUG EFFECTS

针对拓扑异构酶I或II的药物对广泛的人类肿瘤具有活性。稳定共价复合体，将拓扑异构酶转化为DNA损伤，是这些药物杀死细胞的一个重要方面。基因实验已经证明，参与切除修复途径的酶能够与拓扑异构酶I或II形成的共价复合体相互作用。意想不到的是，切除修复基因的突变会导致对拓扑异构酶药物的部分耐药性，这表明共价复合体的加工与拓扑异构酶靶向药物的细胞毒性有关。这项拨款中的实验将检查各种DNA修复途径突变的后果，以确定DNA修复途径如何处理拓扑异构酶介导的DNA损伤。生化实验将测试切除修复机制的哪些组件识别和处理拓扑异构酶介导的DNA损伤。遗传方法将被用来识别其他影响抗拓扑异构酶制剂杀死细胞的DNA修复酶。DNA修复蛋白对拓扑异构酶：DNA共价复合体的处理也可能在拓扑异构酶靶向药物的其他细胞效应中发挥作用。最近的证据表明，依托泊苷和其他拓扑异构酶II靶向药物可以通过产生易位而导致原癌基因的过度表达和激活，从而导致继发性恶性肿瘤。由于喜树碱也会产生高水平的重组，针对拓扑异构酶I的药物也可能导致显著水平的继发性恶性肿瘤。这个项目的一个主要目的是应用酵母模型系统来研究DNA修复功能如何影响针对拓扑异构酶I或H的药物引起的遗传异常的类型和频率。这些实验将提供关于拓扑异构酶抑制剂如何对癌细胞发挥细胞毒作用以及癌细胞如何对这些药物产生耐药性的信息。这些实验对于理解拓扑异构酶靶向药物如何导致继发性恶性肿瘤也将是重要的。

Agents targeting topoisomerase I or II are active against a wide range of human tumors. Stabilization of covalent complexes, converting topoisomerases into DNA damage, is an essential aspect of cell killing by these drugs. Genetic experiments have demonstrated that enzymes that participate in the excision repair pathway are capable of interacting with the covalent complexes formed by either topoisomerase I or II. Unexpectedly, mutations in excision repair genes lead to partial resistance to topoisomerase agents, suggesting that processing of covalent complexes is related to the cytotoxicity of topoisomerase targeting drugs. The experiments in this grant will examine the consequences of mutations in various DNA repair pathways to determine how DNA repair pathways process topoisomerase-mediated DNA damage. Biochemical experiments will test which components of the excision repair machinery recognize and process topoisomerase-mediated DNA damage. Genetic approaches will be used to identify other DNA repair enzymes that influence cell killing by anti-topoisomerase agents. The processing of topoisomerase:DNA covalent complexes by DNA repair proteins may also play a role in the other cellular effects of topoisomerase targeting drugs. Recent evidence has demonstrated that etoposide and other topoisomerase II-targeting drugs can cause secondary malignancies by generating translocations that cause the overexpression and activation of proto-oncogenes. Since camptothecins also generate high levels of recombination, topoisomerase I targeting drugs may also lead to significant levels of secondary malignancies. A major aim of this project is will be to apply a yeast model system to study how DNA repair functions influence the type and frequency of genetic aberrations caused by drugs targeting topoisomerases I or H. These experiments will provide information concerning how topoisomerase inhibitors exert their cytotoxic effects against cancer cells, and how cancer cells may develop resistance to these agents. The experiments will also be important for understanding how topoisomerase targeting drugs lead to secondary malignancies.