Helleman Jozien, Burger Herman, Hamelers Irene H L, Boersma Antonius W M, de Kroon Anton I P M, Stoter Gerrit, Nooter Kees
Department of Medical Oncology, Erasmus MC/Daniel den Hoed Cancer Center, Rotterdam, The Netherlands.
Cancer Biol Ther. 2006 Aug;5(8):943-9. doi: 10.4161/cbt.5.8.2876. Epub 2006 Aug 2.
The effectiveness of platinum drugs in the treatment of cancer is hindered by intrinsic and acquired resistance. The cause of clinical resistance to platinum compounds is still unknown. In an attempt to identify new cellular mechanisms of cisplatin resistance, a one-step cisplatin-selection procedure was used to generate resistant sublines of the platinum sensitive A2780 ovarian cancer cell line. In the present study we selected an A2780 subline, A2780-Pt, that has a significantly reduced ability to accumulate cisplatin (36% of the parent A2780 cell line) and consequently shows a clear cisplatin-resistant phenotype (resistance factor, i.e., RF: 8.6). The A2780-Pt cell line was specifically cross-resistant to carboplatin (RF: 12.0), tetraplatin (RF: 8.1) and oxaliplatin (RF: 6.1) which was associated with a reduced cellular platinum accumulation (50%, 54% and 58% of A2780, respectively). No cross-resistance was found for a variety of other anticancer agents. Further experiments to determine the cause of the platinum resistance of the A2780-Pt cell line revealed that: (1) impaired cellular platinum accumulation could not be attributed to aberrant expression of MRP2 (ABCC2), CTR1 (SLC31A1), ATP7A or ATP7B, (2) resistance was not associated with platinum inactivation by metallothionein and glutathione, (3) the platinum efflux rate was similar to that of A2780, (4) the defect in cellular accumulation and the resistance could be overcome by treatment with cisplatin nanocapsules, consistent with impaired influx, and (5) the defect in accumulation is specific for platinum compounds in the cis-configuration, since A2780-Pt cells did not show reduced accumulation of transplatin. This specificity suggests that not passive diffusion but an inward transporter is impaired in A2780-Pt. In conclusion, we generated an A2780 subline that showed a uniquely stable platinum resistance phenotype, which could theoretically be caused by an impaired inward transporter specific for cis-configurated platinum compounds.
铂类药物在癌症治疗中的有效性受到内在和获得性耐药的阻碍。对铂化合物临床耐药的原因仍不清楚。为了确定顺铂耐药的新细胞机制，采用一步顺铂选择程序来产生铂敏感的A2780卵巢癌细胞系的耐药亚系。在本研究中，我们选择了一个A2780亚系A2780-Pt，其积累顺铂的能力显著降低（为亲本A2780细胞系的36%），因此表现出明显的顺铂耐药表型（耐药因子，即RF：8.6）。A2780-Pt细胞系对卡铂（RF：12.0）、四铂（RF：8.1）和奥沙利铂（RF：6.1）具有特异性交叉耐药，这与细胞内铂积累减少有关（分别为A2780的50%、54%和58%）。对多种其他抗癌药物未发现交叉耐药。进一步确定A2780-Pt细胞系铂耐药原因的实验表明：（1）细胞内铂积累受损不能归因于MRP2（ABCC2）、CTR1（SLC31A1）、ATP7A或ATP7B的异常表达；（2）耐药与金属硫蛋白和谷胱甘肽使铂失活无关；（3）铂流出率与A2780相似；（4）细胞积累缺陷和耐药可通过顺铂纳米胶囊治疗克服，这与流入受损一致；（5）积累缺陷对顺式构型的铂化合物具有特异性，因为A2780-Pt细胞未显示反铂积累减少。这种特异性表明，A2780-Pt中受损的不是被动扩散而是内向转运体。总之，我们产生了一个A2780亚系，其表现出独特稳定的铂耐药表型，理论上这可能是由对顺式构型铂化合物特异的内向转运体受损引起的。
