Chiang C D, Song E J, Yang V C, Chao C C
Department of Internal Medicine, Taichung Veteran General Hospital, Taiwan, Republic of China.
Biochem J. 1994 Aug 1;301 ( Pt 3)(Pt 3):759-64. doi: 10.1042/bj3010759.
A human lung-cancer PC-9 subline with acquired resistance to vincristine (VCR), a chemotherapeutic agent, was established with incremental increases of the drug. The resistant PC-9 subline (PC-9/VCR) shows a 12-fold increase in resistance to VCR and a unique cross-resistance pattern: high cross-resistance to the potent VCR analogue colchicine (6.9-fold) and vinblastine (2.5-fold); lower cross-resistance to actinomycin D (1.8-fold), cisplatin (1.2-fold) and adriamycin (1.3-fold) and a sensitivity to melphalan and VP-16 which is similar to that of the parental cell line. A reduced accumulation of VCR in the resistant cells was demonstrated. Interestingly, the VCR resistance of the PC-9/VCR cell line was partially reversed by ascorbic acid, and the drug uptake was enhanced. In contrast, ascorbic acid had no effect on drug tolerance and drug accumulation was not observed in either PC-9 parental cells or known multidrug-resistant (MDR) cells, suggesting that VCR resistance in PC-9/VCR cells results essentially from reduced drug accumulation. It is worth noting that, whereas reduced drug accumulation in the PC-9/VCR cells was susceptible to modulation by ascorbic acid, the increased efflux rate characteristic of the resistant cells was not. Further, there was a higher efflux rate in resistant cells than in parental cells. DNA Southern- and RNA Northern-blot hybridization analyses indicate that PC-9/VCR cells do not contain amplified mdr genes or overexpress P-glycoprotein. In addition, the calcium-channel blocker verapamil, which acts as a competitive inhibitor of drug binding and efflux, did not affect the resistant phenotype of PC-9/VCR cells. These findings suggest an ascorbic acid-sensitive drug uptake mechanism which is important in mediating VCR resistance per se in human lung-cancer cells; this differs from the P-glycoprotein-mediated MDR mechanism.
通过逐步增加化疗药物长春新碱（VCR）的剂量，建立了一株对VCR产生获得性耐药的人肺癌PC-9亚系。耐药的PC-9亚系（PC-9/VCR）对VCR的耐药性增加了12倍，并呈现出独特的交叉耐药模式：对强效VCR类似物秋水仙碱（6.9倍）和长春碱（2.5倍）具有高度交叉耐药性；对放线菌素D（1.8倍）、顺铂（1.2倍）和阿霉素（1.3倍）的交叉耐药性较低，对美法仑和依托泊苷的敏感性与亲代细胞系相似。结果表明耐药细胞中VCR的蓄积减少。有趣的是，抗坏血酸可部分逆转PC-9/VCR细胞系对VCR的耐药性，并增强药物摄取。相比之下，抗坏血酸对PC-9亲代细胞或已知的多药耐药（MDR）细胞的药物耐受性没有影响，也未观察到药物蓄积，这表明PC-9/VCR细胞对VCR的耐药性主要源于药物蓄积减少。值得注意的是，虽然PC-9/VCR细胞中药物蓄积减少易受抗坏血酸调节，但耐药细胞特征性的外排率增加不受抗坏血酸影响。此外，耐药细胞的外排率高于亲代细胞。DNA Southern杂交和RNA Northern杂交分析表明，PC-9/VCR细胞不含有扩增的mdr基因，也不高表达P-糖蛋白。此外，作为药物结合和外排竞争性抑制剂的钙通道阻滞剂维拉帕米，对PC-9/VCR细胞的耐药表型没有影响。这些发现提示了一种对抗坏血酸敏感的药物摄取机制，该机制在介导人肺癌细胞对VCR的耐药性中起重要作用；这与P-糖蛋白介导的MDR机制不同。
