Kim W J, Kakehi Y, Yoshida O
Department of Urology, College of Medicine, Chungbuk National University, Korea.
Int J Urol. 1997 Nov;4(6):583-90. doi: 10.1111/j.1442-2042.1997.tb00314.x.
Multiple mechanisms are important in multidrug resistance in urothelial cancers. We investigated the acquisition of a multidrug resistance phenotype in human bladder cancer cells exposed to doxorubicin.
Human bladder cancer cell line 5637 and 2 doxorubicin drug-resistant sublines (5637/DR5.5 and 5637/DR50) were used. Measurements were made of the steady state mRNA levels of the multidrug resistance gene (mdr1), multidrug resistance-associated protein (MRP), glutathione-S-transferase-pi and DNA topoisomerase II (topo II) genes, P-glycoprotein (PgP) and MRP expression, glutathione (GSH) and GSH enzyme activity, and topo II catalytic activity. The pharmacokinetics were compared between the parent and the drug-resistant sublines.
5637/DR5.5 and 5637/DR50 cells were 7.6- and 16.2-fold more resistant to doxorubicin and 16.7- and 48.3-fold more resistant to etoposide, respectively, compared with 5637 cells. A dose escalation of doxorubicin increased the MRP expression, GSH levels and glutathione-S-transferase (GST) activity, although no PgP expression was observed in any cell line. Resistance was brought about by decreased drug accumulation through drug efflux, although intracellular daunorubicin concentrations were similar between DR5.5 and DR50 cells. Topo II catalytic activity was undetectable in DR50 cells, but maintained in both the parent and DR5.5 cells.
Reduced drug accumulation in doxorubicin-resistant cells was mediated by MRP instead of PgP indicating that MRP-mediated drug efflux functions in a limited manner for drug resistance. An increase in drug efflux via MRP, reduced topo II activity, and increased GSH levels/GSH-related enzyme activities may play major roles in nonPgP-mediated multidrug resistance in urothelial cancers treated with anthracyclines.
多种机制在尿路上皮癌的多药耐药中起重要作用。我们研究了暴露于阿霉素的人膀胱癌细胞中多药耐药表型的获得情况。
使用人膀胱癌细胞系5637和2个阿霉素耐药亚系（5637/DR5.5和5637/DR50）。对多药耐药基因（mdr1）、多药耐药相关蛋白（MRP）、谷胱甘肽-S-转移酶-pi和DNA拓扑异构酶II（topo II）基因的稳态mRNA水平、P-糖蛋白（PgP）和MRP表达、谷胱甘肽（GSH）和GSH酶活性以及topo II催化活性进行了测量。比较了亲代细胞系和耐药亚系之间的药代动力学。
与5637细胞相比，5637/DR5.5和5637/DR50细胞对阿霉素的耐药性分别高7.6倍和16.2倍，对依托泊苷的耐药性分别高16.7倍和48.3倍。阿霉素剂量递增会增加MRP表达、GSH水平和谷胱甘肽-S-转移酶（GST）活性，尽管在任何细胞系中均未观察到PgP表达。耐药是由于药物外排导致药物蓄积减少引起的，尽管DR5.5和DR50细胞内柔红霉素浓度相似。在DR50细胞中未检测到Topo II催化活性，但在亲代细胞系和DR5.5细胞中均保持。
阿霉素耐药细胞中药物蓄积减少是由MRP而非PgP介导的，这表明MRP介导的药物外排在耐药中起有限作用。通过MRP增加药物外排、降低topo II活性以及增加GSH水平/GSH相关酶活性可能在蒽环类药物治疗的尿路上皮癌非PgP介导的多药耐药中起主要作用。
