Hasinoff B B, Kuschak T I, Creighton A M, Fattman C L, Allan W P, Thampatty P, Yalowich J C
Faculty of Pharmacy, University of Manitoba, Winnipeg, Canada.
Biochem Pharmacol. 1997 Jun 15;53(12):1843-53. doi: 10.1016/s0006-2952(97)00013-0.
A Chinese hamster ovary (CHO) cell line highly resistant to the non-cleavable complex-forming topoisomerase II inhibitor dexrazoxane (ICRF-187, Zinecard) was selected. The resistant cell line (DZR) was 1500-fold resistant (IC50 = 2800 vs 1.8 microM) to continuous dexrazoxane exposure. DZR cells were also cross-resistant (8- to 500-fold) to other bisdioxopiperazines (ICRF-193, ICRF-154, and ICRF-186), and somewhat cross-resistant (4- to 14-fold) to anthracyclines (daunorubicin, doxorubicin, epirubicin, and idarubicin) and etoposide (8.5-fold), but not to the other non-cleavable complex-forming topoisomerase II inhibitors suramin and merbarone. The cytotoxicity of dexrazoxane to both cell lines was unchanged in the presence of the membrane-active agent verapamil. DZR cells were 9-fold resistant to dexrazoxane-mediated inhibition of topoisomerase II DNA decatenation activity compared with CHO cells (IC50 = 400 vs 45 microM), but were only 1.4-fold (IC50 = 110 vs 83 microM) resistant to etoposide. DZR cells contained one-half the level of topoisomerase II protein compared with parental CHO cells. However, the specific activity for decatenation using nuclear extract topoisomerase II was unchanged. Etoposide (100 microM)-induced topoisomerase II-DNA complexes in DZR cells and isolated nuclei were similarly one-half the level found in CHO cells and in isolated nuclei. However, the ability of 500 microM dexrazoxane to inhibit etoposide (100 microM)-induced topoisomerase II-DNA covalent complexes was reduced 4- to 6-fold in both DZR cells and nuclei compared with CHO cells and nuclei. In contrast, there was no differential ability of aclarubicin or merbarone to inhibit etoposide-induced topoisomerase II-DNA complexes in CHO compared with DZR cells and isolated nuclei. It was concluded that the DZR cell line acquired its resistance to dexrazoxane mainly through an alteration in the topoisomerase II target.
筛选出一种对不可裂解的形成复合物的拓扑异构酶II抑制剂右丙亚胺（ICRF - 187，Zinecard）具有高度抗性的中国仓鼠卵巢（CHO）细胞系。该抗性细胞系（DZR）对持续暴露于右丙亚胺具有1500倍的抗性（IC50 = 2800 μM对1.8 μM）。DZR细胞对其他双二氧哌嗪（ICRF - 193、ICRF - 154和ICRF - 186）也具有交叉抗性（8至500倍），对蒽环类药物（柔红霉素、阿霉素、表柔比星和伊达比星）和依托泊苷具有一定程度的交叉抗性（4至14倍），但对其他不可裂解的形成复合物的拓扑异构酶II抑制剂苏拉明和美巴龙不具有交叉抗性。在存在膜活性剂维拉帕米的情况下，右丙亚胺对两种细胞系的细胞毒性没有变化。与CHO细胞相比，DZR细胞对右丙亚胺介导的拓扑异构酶II DNA解连环活性抑制具有9倍的抗性（IC50 = 400 μM对45 μM），但对依托泊苷仅具有1.4倍的抗性（IC50 = 110 μM对83 μM）。与亲代CHO细胞相比，DZR细胞中拓扑异构酶II蛋白水平为其一半。然而，使用核提取物拓扑异构酶II进行解连环的比活性没有变化。依托泊苷（100 μM）在DZR细胞和分离的细胞核中诱导的拓扑异构酶II - DNA复合物同样是CHO细胞和分离细胞核中发现水平的一半。然而，与CHO细胞和细胞核相比，500 μM右丙亚胺抑制依托泊苷（100 μM）诱导的拓扑异构酶II - DNA共价复合物的能力在DZR细胞和细胞核中降低了4至6倍。相比之下，与DZR细胞和分离的细胞核相比，阿克拉霉素或美巴龙抑制CHO细胞中依托泊苷诱导的拓扑异构酶II - DNA复合物的能力没有差异。得出的结论是，DZR细胞系对右丙亚胺的抗性主要是通过拓扑异构酶II靶点的改变获得的。
