Withoff S, de Vries E G, Keith W N, Nienhuis E F, van der Graaf W T, Uges D R, Mulder N H
Department of Internal Medicine, University Hospital Groningen, The Netherlands.
Br J Cancer. 1996 Dec;74(12):1869-76. doi: 10.1038/bjc.1996.647.
Sublines of the human small-cell lung carcinoma (SCLC) cell line GLC4 with acquired resistance to teniposide, amsacrine and mitoxantrone (GLC4/VM20x, GLC4/AM3x and GLC4/MIT60x, respectively) were derived to study the contribution of DNA topoisomerase II alpha and -beta (TopoII alpha and -beta) to resistance for TopoII-targeting drugs. The cell lines did not overexpress P-glycoprotein or the multidrug resistance-associated protein but were cross-resistant to other TopoII drugs. GLC4/VM20x showed a major decrease in TopoII alpha protein (54%; for all assays presented in this paper the GLC4 level was defined to be 100%) without reduction in TopoII beta protein; GLC4/AM3x showed only a major decrease in TopoII beta protein (to 18%) and not in TopoII alpha. In GLC4/MIT60x, the TopoII alpha and -beta protein levels were both decreased (TopoII alpha to 31%; TopoII beta protein was undetectable). The decrease in TopoII alpha protein in GLC4/VM20x and GLC4/MIT60x, was mediated by decreased TopoII alpha mRNA levels. Loss of TopoII alpha gene copies contributed to the mRNA decrease in these cell lines. Only in the GLC4/MIT60x cell line was an accumulation defect observed for the drug against which the cell line was made resistant. In conclusion, TopoII alpha and -beta levels were decreased differentially in the resistant cell lines, suggesting that resistance to these drugs may be mediated by a decrease in a specific isozyme.
为了研究DNA拓扑异构酶IIα和-β（TopoIIα和-β）对靶向TopoII药物耐药性的影响，我们构建了人小细胞肺癌（SCLC）细胞系GLC4对替尼泊苷、安吖啶和米托蒽醌产生获得性耐药的亚系（分别为GLC4/VM20x、GLC4/AM3x和GLC4/MIT60x）。这些细胞系未过度表达P-糖蛋白或多药耐药相关蛋白，但对其他TopoII药物具有交叉耐药性。GLC4/VM20x的TopoIIα蛋白显著减少（54%；本文所有实验中GLC4水平定义为100%），而TopoIIβ蛋白未减少；GLC4/AM3x仅TopoIIβ蛋白显著减少（降至18%），TopoIIα蛋白未减少。在GLC4/MIT60x中，TopoIIα和-β蛋白水平均降低（TopoIIα降至31%；TopoIIβ蛋白检测不到）。GLC4/VM20x和GLC4/MIT60x中TopoIIα蛋白的减少是由TopoIIα mRNA水平降低介导的。TopoIIα基因拷贝数的丢失导致了这些细胞系中mRNA的减少。仅在GLC4/MIT60x细胞系中观察到对其产生耐药性的药物存在蓄积缺陷。总之，耐药细胞系中TopoIIα和-β水平差异降低，表明对这些药物的耐药性可能由特定同工酶的减少介导。
