DNA REPAIR AND ANTITOPOISOMERASE DRUG EFFECTS

靶向拓扑异构酶I或II的药物对多种人类肿瘤具有活性。共价复合物的稳定，将拓扑异构酶转化为DNA损伤，是这些药物杀死细胞的重要方面。遗传实验表明，参与切除修复途径的酶能够与拓扑异构酶I或拓扑异构酶II形成的共价复合物相互作用。出乎意料的是，切除修复基因的突变导致对拓扑异构酶药物的部分耐药，这表明共价复合物的加工与拓扑异构酶靶向药物的细胞毒性有关。本资助的实验将检查各种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成部分识别和处理拓扑异构酶介导的DNA损伤。遗传方法将用于鉴定其他DNA修复酶，这些酶会影响抗拓扑异构酶药物对细胞的杀伤。DNA修复蛋白对拓扑异构酶：DNA共价复合物的加工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靶向拓扑异构酶ii的药物可通过产生易位导致原癌基因的过度表达和激活而导致继发性恶性肿瘤。由于喜树碱也产生高水平的重组，拓扑异构酶I靶向药物也可能导致显著水平的继发性恶性肿瘤。该项目的一个主要目的是应用酵母模型系统来研究DNA修复功能如何影响靶向拓扑异构酶I或h的药物引起的遗传畸变的类型和频率。这些实验将提供拓扑异构酶抑制剂如何对癌细胞发挥细胞毒性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很重要。

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.