Charcosset J Y, Saucier J M, Jacquemin-Sablon A
Unité de Biochimie et Enzymologie (UA 147 CNRS), Institut Gustave Roussy, Villejuif, France.
Biochem Pharmacol. 1988 Jun 1;37(11):2145-9. doi: 10.1016/0006-2952(88)90573-4.
We have isolated a Chinese hamster lung cell line resistant to 9-hydroxyellipticine (DC-3F/9-OH-E) which is also cross-resistant to topoisomerase II inhibitors such as amsacrine and etoposide. In this work we have studied quantitatively both DNA topoisomerase II activity by decatenation of kinetoplast DNA and drug-stimulated DNA cleavage of pBR 322. DNA topoisomerase II activity of DC-3F/9-OH-E nuclear extract was reduced by 3.5-fold as compared to that from DC-3F (sensitive parent) nuclear extract. We also found that DC-3F/9-OH-E nuclear extracts have a reduced capacity to induce in vitro topoisomerase II-mediated DNA cleavage upon stimulation by etoposide and amsacrine (7- and 10-fold respectively). Besides, mixing nuclear extracts from both sensitive and resistant cells indicates that either the enzyme in resistant cells is modified or a modulating factor is associated to it. Our results suggest that the resistance of the DC-3F/9-OH-E cell line to topoisomerase II inhibitors might be due to both a reduced amount of the enzyme and its reduced ability to form the cleavable complex in the presence of drugs.
我们分离出了一种对9-羟基玫瑰树碱具有抗性的中国仓鼠肺细胞系（DC-3F/9-OH-E），该细胞系对拓扑异构酶II抑制剂如安吖啶和依托泊苷也具有交叉抗性。在这项研究中，我们通过解开动质体DNA定量研究了DNA拓扑异构酶II的活性，并对pBR 322进行了药物刺激的DNA切割实验。与DC-3F（敏感亲本）细胞核提取物相比，DC-3F/9-OH-E细胞核提取物的DNA拓扑异构酶II活性降低了3.5倍。我们还发现，在依托泊苷和安吖啶刺激下（分别降低7倍和10倍），DC-3F/9-OH-E细胞核提取物诱导体外拓扑异构酶II介导的DNA切割的能力降低。此外，将敏感细胞和抗性细胞的细胞核提取物混合表明，抗性细胞中的酶要么被修饰，要么有一个调节因子与其相关。我们的结果表明，DC-3F/9-OH-E细胞系对拓扑异构酶II抑制剂的抗性可能是由于该酶的量减少以及在药物存在下形成可切割复合物的能力降低所致。
