Katschinski D M, Robins H I
Institute of Physiology, Medical University of Lübeck, Germany.
Int J Cancer. 1999 Jan 5;80(1):104-9. doi: 10.1002/(sici)1097-0215(19990105)80:1<104::aid-ijc20>3.0.co;2-a.
The effect of different temperatures (37-42.5 degrees C) on SN-38 (the active metabolite of CPT-11) cytotoxicity was examined in the human lung carcinoma cell lines H460 and Calu-6 as well as the murine fibrosarcoma cell line L929. The cytotoxicity of SN-38, determined by MTT cell survival assay, was significantly increased in each cell line in combination with 41.8 degrees C hyperthermia (x60-120 min); the combination of SN-38 with 40.5 degrees C and 42.5 degrees C, however, was unchanged compared to 37 degrees C. Determination of topoisomerase (Topo) I DNA cross-linking in Calu-6 cells and L929 cells after treatment with SN-38 showed the same temperature profile as seen in the cell-survival assays with increased Topo I DNA cross-linking after treatment with the combination of SN-38 and 41.8 degrees C hyperthermia and unchanged Topo I DNA cross-linking at 40.5 degrees C and 42.5 degrees C. To test the hypothesis that increased Topo I DNA cross-linking and SN-38 cytotoxicity at 41.8 degrees C is caused by hyperthermia-modulated changes in Topo I activity, catalytic activity of Topo I extracted from each cell line and of purified human Topo I was determined at 20-42.5 degrees C. Topo I activity was found to be gradually increased with rising temperatures, resulting in significantly higher activity at 41.8 degrees C compared to 37 degrees C; further increase of temperature past 41.8 degrees C decreased Topo I activity back to levels found at 37 degrees C. Our data are used to explain a series of events resulting in hyperthermic enhancement of Topo I DNA cross-linking and SN-38 cytotoxicity in combination with 41.8 degrees C hyperthermia via increased Topo I activity.
在人肺癌细胞系H460和Calu - 6以及小鼠纤维肉瘤细胞系L929中，研究了不同温度（37 - 42.5摄氏度）对SN - 38（CPT - 11的活性代谢产物）细胞毒性的影响。通过MTT细胞存活试验测定，SN - 38的细胞毒性在每个细胞系中与41.8摄氏度热疗（60 - 120分钟）联合时显著增加；然而，SN - 38与40.5摄氏度和42.5摄氏度联合时，与37摄氏度相比无变化。在用SN - 38处理Calu - 6细胞和L929细胞后，测定拓扑异构酶（Topo）I DNA交联情况，其温度变化情况与细胞存活试验相同，即SN - 38与41.8摄氏度热疗联合处理后Topo I DNA交联增加，而在40.5摄氏度和42.5摄氏度时Topo I DNA交联无变化。为了验证41.8摄氏度时Topo I DNA交联增加和SN - 38细胞毒性增强是由热疗调节的Topo I活性变化所致这一假设，在20 - 42.5摄氏度下测定了从每个细胞系中提取的Topo I以及纯化的人Topo I的催化活性。发现Topo I活性随温度升高而逐渐增加，与37摄氏度相比，在41.8摄氏度时活性显著更高；温度超过41.8摄氏度进一步升高会使Topo I活性降至37摄氏度时的水平。我们的数据用于解释一系列事件，即通过增加Topo I活性，41.8摄氏度热疗联合导致Topo I DNA交联和SN - 38细胞毒性的热增强。
