Binaschi M, Capranico G, De Isabella P, Mariani M, Supino R, Tinelli S, Zunino F
Division of Experimental Oncology B, Istituto Nazionale per lo Studio e la Cura dei Tumori, Milan, Italy.
Int J Cancer. 1990 Feb 15;45(2):347-52. doi: 10.1002/ijc.2910450223.
In an attempt to clarify the role of drug-induced protein-associated DNA breaks (i.e., DNA topoisomerase II-mediated DNA cleavage) in the cytotoxic activity of doxorubicin and etoposide, their cellular effects were compared in 2 human small-cell lung cancer (SCLC) lines, characterized by differential sensitivity to DNA topoisomerase II inhibitors. These drugs were selected for comparative studies since they are among the most effective agents in the treatment of SCLC. H146 and N592 cell lines were obtained from pleural effusion and bone-marrow aspirate of pretreated patients, respectively. Both cell lines grew as floating aggregates with similar doubling times (30 and 33 hr for N592 and H146 cells, respectively). Although, immediately after 1 hr exposure to equitoxic drug levels, the extent of DNA cleavage produced by doxorubicin was markedly lower than that produced by etoposide, DNA lesions produced by doxorubicin persisted and even increased following drug removal. In contrast, an almost complete disappearance of etoposide-induced DNA breaks was noted 1 hr after drug removal. Resealing of strand breaks was faster in N592 than in H146 cells. These findings suggest that reversal of these lesions plays a major role in cell survival rather than the occurrence of DNA breaks immediately following drug exposure. This observation is consistent with the view that inhibition of DNA re-ligation rather than stimulation of DNA cleavage is the critical step for drug action. The different response of these cell lines to cytotoxic action of the topoisomerase inhibitors is associated with a differential drug effect on DNA integrity (detected as DNA double-strand breaks and DNA-protein cross-links). However DNA lesions were comparable when cells were exposed to equitoxic drug levels. The observation that etoposide-induced DNA breaks were similar in isolated nuclei from both cell lines suggests that drug-target interaction is modulated in a different manner in the intact cell. As indicated by doxorubicin uptake and retention, cellular drug pharmacokinetics do not account for the different drug response of the studied SCLC lines, presumably, reflecting a different extent of DNA break formation and/or a different cytotoxic consequence of DNA damage.
为了阐明药物诱导的蛋白质相关DNA断裂（即DNA拓扑异构酶II介导的DNA切割）在阿霉素和依托泊苷细胞毒性活性中的作用，在2个人类小细胞肺癌（SCLC）细胞系中比较了它们的细胞效应，这两个细胞系对DNA拓扑异构酶II抑制剂具有不同的敏感性。选择这些药物进行比较研究是因为它们是治疗SCLC最有效的药物之一。H146和N592细胞系分别从预处理患者的胸腔积液和骨髓穿刺物中获得。两个细胞系均以漂浮聚集体的形式生长，倍增时间相似（N592和H146细胞分别为30和33小时）。尽管在暴露于等毒性药物水平1小时后，阿霉素产生的DNA切割程度明显低于依托泊苷产生的程度，但阿霉素产生的DNA损伤在药物去除后持续存在甚至增加。相反，在药物去除1小时后，观察到依托泊苷诱导的DNA断裂几乎完全消失。N592细胞中链断裂的重新封闭比H146细胞更快。这些发现表明，这些损伤的逆转在细胞存活中起主要作用，而不是药物暴露后立即发生的DNA断裂。这一观察结果与以下观点一致，即抑制DNA重新连接而不是刺激DNA切割是药物作用的关键步骤。这些细胞系对拓扑异构酶抑制剂细胞毒性作用的不同反应与药物对DNA完整性的不同影响有关（检测为DNA双链断裂和DNA-蛋白质交联）。然而，当细胞暴露于等毒性药物水平时，DNA损伤是相当的。两个细胞系分离细胞核中依托泊苷诱导的DNA断裂相似的观察结果表明，在完整细胞中药物-靶点相互作用以不同方式被调节。如阿霉素摄取和保留所示，细胞药物药代动力学不能解释所研究的SCLC细胞系不同的药物反应，大概反映了DNA断裂形成的不同程度和/或DNA损伤的不同细胞毒性后果。
