Teniposide-resistant CEM cells, which express mutant DNA topoisomerase II alpha, when treated with non-complex-stabilizing inhibitors of the enzyme, display no cross-resistance and reveal aberrant functions of the mutant enzyme.
Teniposide-resistant CEM cells, which express mutant DNA topoisomerase II alpha, when treated with non-complex-stabilizing inhibitors of the enzyme, display no cross-resistance and reveal aberrant functions of the mutant enzyme.
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发表时间：
1993-12
期刊：
影响因子：
11.2
通讯作者：
Mei Chen;William T. Beck
中科院分区：
文献类型：
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作者：
Mei Chen;William T. Beck
我们已经研究了一组DNA拓扑异构酶II（topo II）抑制剂，甲基巴龙，阿克拉维汀，SN 22995，RP 60475 F，和fostriecin，在CCRF-CEM细胞和两个亚系，CEM/VM-1和CEM/VM-1-5，选择增加耐药性替尼泊苷（VM-26）的影响。替尼泊苷耐药亚系被称为“at-MDR”，用于改变拓扑异构酶II相关的多药耐药。这些拓扑异构酶II抑制剂不同于“经典”抑制剂如替尼泊苷，因为它们不稳定DNA-topo II复合物。在这项研究中，我们发现我们的at-MDR细胞系对这些“非经典”topo II抑制剂表达很少或没有交叉耐药性。Merbarone和SN 22995仅在VM-26之前加入时才能抑制CEM细胞中VM-26介导的DNA-topo II复合物。由于它们不消耗topo II蛋白，这表明这些药物可能在酶与DNA结合之前抑制topo II活性，从而防止VM-26介导的topo II-DNA复合物的稳定。CEM细胞连续暴露于甲基巴龙、SN 22995或VM-26引起G2期阻滞，如通过流式细胞术测定的。同样地，用VM-26连续处理的at-MDR细胞也停滞在G2。相比之下，用甲基巴龙或SN 22995处理的at-MDR细胞产生了质的不同的模式; at-MDR细胞首先在G2中积累，但随后逃脱了G2阻滞，并进入有丝分裂，染色体延长并缠结，但未能分裂。然而，它们的DNA被重新复制，细胞最终积累在8 N DNA阶段。鉴于野生型和突变型topo II α等位基因在at-MDR细胞中表达（B. Y. Bugg，M. K.丹克斯，W. T. Beck和D. P. Suttle突变型DNA拓扑异构酶II在替尼泊苷耐药的CCRF-CEM人白血病细胞中的表达Proc. Natl. Acad. Sci.美国，88：7654-7658，1991），我们假设药物如美巴龙可抑制野生型拓扑异构酶II α的活性，从而在染色体凝聚和姐妹染色单体分离期间揭示突变酶的异常活性。
We have examined the effects of a group of DNA topoisomerase II (topo II) inhibitors, merbarone, aclarubicin, SN22995, RP60475F, and fostriecin, in CCRF-CEM cells and two sublines, CEM/VM-1 and CEM/VM-1-5, that were selected for increasing resistance to teniposide (VM-26). The teniposide-resistant sublines have been termed "at-MDR" for altered topo II-associated multidrug resistance. These topo II inhibitors differ from the "classic" inhibitors such as teniposide in that they do not stabilize DNA-topo II complexes. In this study, we found that our at-MDR cell lines express little or no cross-resistance to these "non-classic" topo II inhibitors. Merbarone and SN22995 inhibited VM-26-mediated DNA-topo II complexes in CEM cells only when they were added before VM-26. Since they did not deplete topo II protein, it suggested that these drugs may inhibit topo II activity before the enzyme binds to DNA, thereby preventing stabilization of VM-26-mediated topo II-DNA complexes. Continuous exposure of CEM cells to merbarone, SN22995, or VM-26 caused G2 arrest, as determined by flow cytometry. Likewise, at-MDR cells continuously treated with VM-26 also arrested in G2. By contrast, treatment of at-MDR cells with either merbarone or SN22995 produced a qualitatively different pattern; the at-MDR cells first accumulated in G2 but then escaped the G2 block and proceeded into mitosis with elongated and intertwined chromosomes but failed to divide. Their DNA was re-replicated, however, and the cells eventually accumulated at the 8N DNA stage. Given that both wild-type and mutant topo II alpha alleles are expressed in the at-MDR cells (B. Y. Bugg, M. K. Danks, W. T. Beck, and D. P. Suttle. Expression of a mutant DNA topoisomerase II in CCRF-CEM human leukemic cells selected for resistance to teniposide. Proc. Natl. Acad. Sci. USA, 88: 7654-7658, 1991), we hypothesize that drugs such as merbarone may inhibit the activity of wild-type topo II alpha, allowing the aberrant activity of the mutant enzyme to be revealed during chromosome condensation and sister chromatid segregation.