Snyder R D
Abbott Laboratories, Abbott Park, Illinois, USA.
Environ Mol Mutagen. 2000;35(1):13-21.
Determination of the clastogenic potential of new chemical entities, particularly pharmaceuticals, is an important part of the overall safety assessment of such drugs. It is appreciated that clastogenicity can arise from perturbation of many different cellular processes distinct from direct DNA/drug interactions. One such alternative clastogenic process is inhibition of DNA topoisomerase II, during which process the topoisomerase/DNA/drug ternary complex forms stable DNA double-strand breaks (cleavable complex), which become templates for recombinational, mutagenic, and chromosomal fragmentation events. Without extensive experimentation, it is generally not possible to distinguish clastogenicity arising from direct drug/DNA interaction from that arising from inhibition of topoisomerase II. In the present investigation, we demonstrate that specific catalytic inhibitors of DNA topoisomerase II reduce the clastogenicity of topoisomerase poisons but not that arising via non-topoisomerase-dependent mechanisms. In particular, it is shown that catalytic topoisomerase II inhibitors such as chloroquine, sodium azide, and A-74932, as well as certain intercalating agents such as 9-aminoacridine and ethidium bromide, strongly antagonize the formation of micronuclei induced by the DNA gyrase inhibitor clinafloxacin and the antitumor topoisomerase II poison etoposide. These catalytic inhibitors are also shown to antagonize the clastogenicity of experimental compounds and novel pharmaceuticals presumed to be DNA intercalating agents by virtue of their response in a cell-based bleomycin amplification assay. We extend our previous hypothesis, suggesting that the clastogenicity of some nonstructurally alerting drugs may be due to an as yet unappreciated propensity for DNA intercalation. It is further proposed that intercalation-dependent inhibition of DNA topoisomerase II may be responsible for this clastogenicity and that this may be detected in intact mammalian cells with the use of catalytic topoisomerase inhibitors.
确定新化学实体尤其是药物的致断裂潜力，是此类药物整体安全性评估的重要组成部分。人们认识到，致断裂性可能源于许多与直接DNA/药物相互作用不同的细胞过程的扰动。一种这样的替代性致断裂过程是DNA拓扑异构酶II的抑制，在此过程中拓扑异构酶/DNA/药物三元复合物形成稳定的DNA双链断裂（可切割复合物），其成为重组、诱变和染色体断裂事件的模板。如果没有广泛的实验，通常不可能区分由直接药物/DNA相互作用引起的致断裂性与由拓扑异构酶II抑制引起的致断裂性。在本研究中，我们证明DNA拓扑异构酶II的特异性催化抑制剂降低了拓扑异构酶毒物的致断裂性，但不会降低通过非拓扑异构酶依赖性机制产生的致断裂性。特别是，已表明催化性拓扑异构酶II抑制剂如氯喹、叠氮化钠和A-74932，以及某些嵌入剂如9-氨基吖啶和溴化乙锭，强烈拮抗DNA促旋酶抑制剂环丙沙星和抗肿瘤拓扑异构酶II毒物依托泊苷诱导的微核形成。这些催化抑制剂还显示出拮抗实验化合物和新型药物的致断裂性，这些化合物和药物由于其在基于细胞的博来霉素扩增试验中的反应而被推测为DNA嵌入剂。我们扩展了我们先前的假设，表明一些无结构警示性药物的致断裂性可能归因于尚未认识到的DNA嵌入倾向。进一步提出，依赖嵌入的DNA拓扑异构酶II抑制可能是这种致断裂性的原因，并且这可以在完整的哺乳动物细胞中使用催化性拓扑异构酶抑制剂进行检测。
