PROTEIN-ASSOCIATED DNA BREAKS AS INDICATOR OF TOPOISOMERASE INHIBITION

DNA拓扑异构酶是癌症化疗的主要靶点。拓扑异构酶 I集中在核仁中，拓扑异构酶II是 间期核和中期染色体的核支架 脚手架。染色体分离需要拓扑异构酶II的活性 在有丝分裂期间，这两种酶都参与了DNA代谢。 喜树碱抑制拓扑异构酶I和DNA嵌入物(氨苯西林， 去甲基鬼臼毒素(VP-16和Vm-26)抑制 拓扑异构酶II.酶抑制是由酶连接的DNA断裂引起的， 据信这是药物最初的细胞毒性损伤。 然而，在药物清除后，断裂很快就会逆转。这促使我们 拓扑异构酶连锁脱氧核糖核酸对S细胞毒性损伤的检测 休息一下。我们发现，拓扑异构酶I-DNA复合体是由 喜树碱可能通过与细胞因子相互作用杀死快速增殖的细胞 DNA复制复合体。我们还确定， 拓扑异构酶介导的DNA断裂对已经被 缺钙的。我们已经证实了我们之前的发现 通过暴露于阿霉素而选择的多效性耐药细胞系 对其他拓扑异构酶II抑制剂交叉耐药，并同时具有这两种药物 增加P-糖蛋白和修饰的拓扑异构酶II。此外，我们 发现对长春新碱耐药的细胞增加了 不含耐药拓扑异构酶II的P-糖蛋白。 两种形式的DNA拓扑异构酶I受信号调控的证据 信号转导途径包括蛋白激酶C。

DNA topoisomerases are major targets for cancer chemotherapy. Topoisomerase I is concentrated in nucleoli and topoisomerase II is a major component of the nuclear scaffold for interphase nuclei and of the metaphase chromosome scaffold. Topoisomerase II activity is required for chromosome segregation during mitosis and both enzymes are involved in DNA metabolism. Camptothecin inhibits topoisomerase I, and DNA intercalators (amsacrine, anthracyclines) and demethylepipodophyllotoxins (VP-16 & VM-26) inhibit topoisomerase II. Enzyme inhibition results from enzyme-linked DNA breaks, which are believed to be the initial cytotoxic lesions of the drugs. However, the breaks reverse quickly upon drug removal. This prompted us to determine the cytotoxic lesion(s) induced by the topoisomerase-linked DNA breaks. We have found that the topoisomerase I-DNA complexes induced by camptothecin probably kill rapidly proliferative cells by interacting with DNA replication complexes. We have also determined that topoisomerase-mediated DNA breaks are not toxic in cells which have been depleted of calcium. We have confirmed our previous finding that pleiotropic resistant cell lines selected by exposure to adriamycin are cross-resistant to other topoisomerase II inhibitors and have both increased P-glycoprotein and modified topoisomerase II. In addition, we have found that cells selected for resistance to vincristine have increased P-glycoprotein without drug-resistant topoisomerase II. Finally, we found evidence that two forms of DNA topoisomerase I are regulated by signal transduction pathways including protein kinase C.