功劳木中异汉防己碱对P-糖蛋白介导的人乳腺癌细胞多药耐药性的逆转作用

摘要

本文探讨了异汉防己碱对P-糖蛋白(P-gp)介导的人乳腺癌细胞多药耐药性的逆转作用.首先以RT-PCR和免疫组化方法分别从RNA和蛋白水平检测MCF-7/DOX细胞P-gP表达情况,以明确MCF-7/DOX细胞的耐药特征;然后采用MTT法检测异汉防己碱的内在细胞毒性及其对阿霉素(DOX)的增敏作用,并以RF(reversal fold)值评价其逆转效果:同时应用流式细胞仪(FCM)对细胞内DOX的蓄积量进行了分析;再以免疫组化方法检测异汉防己碱对MCF-7/DOX细胞P-gp表达水平的影响;最后采用罗丹明蓄积和外排试验检测了异汉防己碱对P-gp功能的影响.整个试验以维拉帕米作为阳性对照.实验结果表明:MCF-7/DOX细胞是具有多药耐药表型且P-gp表达阳性的细胞株;无毒剂量异汉防己碱可明显增强DOX对MCF-7/DOX细胞的细胞毒性(RF=3.89),明显高于维拉帕米(RF=2.54)的逆转活性(P＜0.05),但其几乎不影响DOX对MCF-7细胞的抑制作用;异汉防己碱对MCF-7/DOX细胞P-gp表达水平无明显影响,但其可有效抑制P-gp的药物外排功能.因此,异汉防己碱可有效逆转P-gp介导的人乳腺癌细胞的多药耐药性,它可能成为有效多药耐药逆转剂的候选药物.%This study investigated the reversal effect of isotetrandrine, an isoquinoline alkaloid extracted from Caulis mahoniae, on P-glyeoprotein-mediated multidrug resistance in human breast cancer doxorubicin-resistant (MCF-7/DOX) cells. RT-PCR assay and immunity histochemistry assay were used to determine the expression level of mdrl gene and P-gp in MCF-7/DOX cells to elucidate resistant character of MCF-7/DOX cells. The activity of isotetrandine to enhance doxorubicin cytotoxicity was tested using MTT (3-(4,5-dimethyhhiazol)-2,5-diphenyltetrazolium bromide) assay and was evaluated by the reversal fold (RF) values. Intracellular accumulation of doxorubicin was assessed by the determination of doxorubicin-assoeiated fluorescence intensity. Effect of isotetrandrine on the expression level of P-gp in MCF-7/DOX cells was then determined by immunity histochemistry assay. The ability of isotetrandrine to inhibit P-gp function was evaluated by detecting the accumulation and efflux of rhodamine123 ( Rh123 )with flow cytometry (FCM). Verapamil was employed as a comparative agent in whole experiment. The results indicated that MCF-7/DOX cells had phenotype of MDR and that the positive expression of P-gp MCF-7/DOX cells and reversal fold (RF) was significantly higher than that of verapamil (P < 0.05 ), butit hardly affected cytotoxicity of DOX in MCF-7 cells and the expression level of P-gp in MCF-7/DOXcells. The ability of isotetrandrine to inhibit P-gp function was reversible, because incubation of MCF-7/DOX cells with isotetrandrine caused a marked increase in uptake and a notable decrease in efflux of Rh123 and a marked increase of intracellular DOX concentrations. In conclusion, isotetrandrine exhibited potent effect on the reversal of P-gp-mediated MDR in vitro, suggesting that it might become a candidate of effective MDR reversing agent in cancer chemotherapy.