Fattman C L, Allan W P, Hasinoff B B, Yalowich J C
Department of Pharmacology, University of Pittsburgh School of Medicine, PA 15261, USA.
Biochem Pharmacol. 1996 Aug 23;52(4):635-42. doi: 10.1016/0006-2952(96)00338-3.
Etoposide (VP-16)-resistant K562 cells (K/VP.5) were 26-fold resistant to VP-16, due in part to a reduction in DNA topoisomerase II (topoisomerase II) protein levels. Compared with parental K562 cells, VP-16-resistant K/VP.5 cells were found to be 3.4-fold more sensitive to the effects of dexrazoxane (ICRF-187), a topoisomerase II inhibitor that does not stabilize topoisomerase II-DNA covalent complexes. In contrast, K/VP.5 cells were 4.0-fold cross-resistant to merbarone and showed no cross-resistance to fostriecin, two other topoisomerase II inhibitors that do not stabilize topoisomerase II-DNA covalent complexes. Preincubation with ICRF-187 resulted in greater inhibition of subsequent VP-16-induced topoisomerase II-DNA covalent complexes in K/VP.5 cells than in K562 cells. Conversely, preincubation with merbarone resulted in less inhibition of VP-16-induced topoisomerase II-DNA covalent complexes in K/VP.5 cells than in parental K562 cells. Preincubation with forstriecin had little effect on VP-16-induced topoisomerase II-DNA covalent complex formation in either cell line. The onset rates for ICRF-187 inhibition of VP-16-induced topoisomerase II-DNA complex formation were similar in sensitive and resistant cells. In addition, ICRF-187 had a comparable concentration-dependent inhibitory effect on the topoisomerase II catalytic activities of K562 and K/VP.5 cells. Together, our results indicate that collateral sensitivity to ICRF-187 in K/VP.5 cells is due to decreased topoisomerase II protein levels rather than to an alteration in topoisomerase II activity. Furthermore, results suggest that ICRF-187, merbarone, and fostriecin have different mechanisms of action that can be studied effectively in K/VP.5 and K562 cells.
依托泊苷（VP - 16）耐药的K562细胞（K/VP.5）对VP - 16的耐药性是26倍，部分原因是DNA拓扑异构酶II（拓扑异构酶II）蛋白水平降低。与亲代K562细胞相比，发现VP - 16耐药的K/VP.5细胞对右丙亚胺（ICRF - 187）的作用敏感性高3.4倍，右丙亚胺是一种拓扑异构酶II抑制剂，它不会稳定拓扑异构酶II - DNA共价复合物。相比之下，K/VP.5细胞对美巴龙有4.0倍的交叉耐药性，对福司曲星没有交叉耐药性，福司曲星是另外两种不会稳定拓扑异构酶II - DNA共价复合物的拓扑异构酶II抑制剂。用ICRF - 187预孵育导致K/VP.5细胞中随后VP - 16诱导的拓扑异构酶II - DNA共价复合物的抑制作用比K562细胞中更强。相反，用美巴龙预孵育导致K/VP.5细胞中VP - 16诱导的拓扑异构酶II - DNA共价复合物的抑制作用比亲代K562细胞中更小。用福司曲星预孵育对两种细胞系中VP - 16诱导的拓扑异构酶II - DNA共价复合物形成几乎没有影响。ICRF - 187对VP - 16诱导的拓扑异构酶II - DNA复合物形成的抑制起始速率在敏感细胞和耐药细胞中相似。此外，ICRF - 187对K562和K/VP.5细胞的拓扑异构酶II催化活性具有相当的浓度依赖性抑制作用。总之，我们的结果表明，K/VP.5细胞对ICRF - 187的 collateral敏感性是由于拓扑异构酶II蛋白水平降低，而不是拓扑异构酶II活性改变。此外，结果表明ICRF - 187、美巴龙和福司曲星具有不同的作用机制，可在K/VP.5和K562细胞中有效研究。
