TOPOISOMERASE II AS TARGET OF ACTION OF ANTICANCER DRUG

DNA拓扑异构酶II（topo II）导致DNA断裂和DNA- 在哺乳动物细胞暴露于 抗肿瘤DNA嵌入剂（阿霉素、安吖啶、椭圆藤碱） 和去甲基表鬼臼毒素（VP-16，VM-26）。 Topo II可以 从小鼠白血病L1210和中国仓鼠肺纯化 通过FPLC检测成纤维细胞（DC 3F和DC 3F/9-OHE）的生长。 我们已经表明 以前，药物诱导的DNA断裂和DNA蛋白 交联可以在纯化的系统中再现。 了一种方法 已经开发了一种可以绘制药物诱导的拓扑异构酶II- 介导的DNA断裂位点， 琼脂糖或测序凝胶，放射自显影和计算机 分析. 药物诱导的DNA切割位点被定位在 SV40 DNA 药物似乎可以增强DNA在 这些已经被topo II单独切割过了。 每种化学类别 拓扑异构酶II抑制剂表现出选择性增强模式。 在 安吖啶衍生物的情况下，DNA嵌入不是 与topo II抑制效力和DNA序列相关 结合的选择性不影响切割模式。 因此，拓扑异构酶对DNA切割位点的差异增强 II抑制剂可以解释差异药物细胞毒性。 第二 研究类型是研究DNA凹槽的影响 在拓扑二上的粘合剂。 多胺（精胺，亚精胺） 显示调节拓扑异构酶II DNA催化活性和药物- 诱导拓扑异构酶II断裂。 小沟结合剂的DNA结合， 偏端霉素被证明可以改变药物诱导的分布。 拓扑异构酶II介导的DNA断裂。 最后，药物对纯化的 Topo I也被研究过。 DNA嵌入剂似乎是抑制剂 拓扑异构酶I的这种作用可能有助于抗肿瘤活性的 这些药物。

DNA topoisomerases II (topo II) cause the DNA breaks and DNA- protein crosslinks observed upon exposure of mammalian cells to antitumor DNA intercalators (adriamycin, amsacrine, ellipticine) and demethylepipodophyllotoxins (VP-16, VM-26). Topo II can be purified from mouse leukemia L1210 and Chinese hamster lung fibroblasts (DC3F and DC3F/9-OHE) by FPLC. We have shown previously that drug-induced DNA breaks and DNA-protein crosslinks can be reproduce in purified systems. A method has been developed which allows the mapping of drug-induced topo II- mediated DNA break sites by using (32P)-end labeled DNAs, agarose or sequencing gels, autoradiography and computer analysis. Drug-induced DNA cleavage sites were mapped within SV40 DNA. Drugs appeared to enhance DNA cleavage at sites that were already cut by topo II alone. Each chemical class of topo II inhibitors exhibited a selective enhancement pattern. In the case of amsacrine derivatives, DNA intercalation was not correlated with topo II inhibition potency and DNA sequence selectively of binding did not influence the cleavage pattern. Thus the differential enhancement of DNA cleavage sites by topo II inhibitors may explain differential drug cytotoxicity. A second type of studies was to investigate the effects of DNA groove binders upon topo II. Polyamines (spermine, spermidine) were shown to modulate topo II DNA catalytic activities and drug- induced topo II breaks. DNA binding of the minor groove binder, distamycin was shown to change the distribution of drug-induced topo II-mediated DNA breaks. Finally, drug effects upon purified topo I were also studied. DNA intercalators appear to inhibitors topo I and this effect may contribute to the antitumor activity of these drugs.