P─糖蛋白过表达不能完全解释MDR细胞株K562／Dox的抗药性

REDUCED INTRACELLULAR DRUG ACCUMULATION RELATED TO OVEREXPRESSION OF P-GLYCOPROTEIN CAN NOT EXPLAIN THE COMPLETE DRUG RESISTANCE IN MDR CELL VARIANT K562/Dox

本研究探讨ＭＤＲ细胞内药物积聚减少究竟决定其抗药性的多大比例。ＭＤＲ细胞Ｋ５６２／Ｄｏｘ来源于反复用Ｄｏｘ处理人红白血病细胞株Ｋ５６２细胞。经ＭＴＴ法测定，ｋ５６２／Ｄｏｘ对长春新碱等７种抗癌药的抗性提高了１２００～１１倍不等。ｋ５６２／Ｄｏｘ可枝抗人Ｐ－ｇｐ单抗ＪＳＢ－１标记，表明其有Ｐ－ｇｐ高表达。细胞内药物积聚试验显示，Ｋ５６２／Ｄｏｘ细胞内３种蒽坏类药阿霉素、表阿霉素和柔红霉素的积聚均显著低于其药敏细胞Ｋ５６２（Ｐ＜００１）。当Ｋ５６２／Ｄｏｘ与１．７２μｍｏｌ／Ｌ或８．６２μｍｏｌ／Ｌ的阿霉素（表阿霉素或柔红霉素）温育时，可使其细胞内的药物积聚饮复正常的Ｖｅｒ浓度分别为６μｍｏｌ／Ｌ或１２μｍｏｌ／Ｌ，提示使ＭＤＲ细胞内药物积聚恢复依赖于Ｖｅｒ与药物的相对浓度。然而，当Ｖｅｒ浓度为６μｍｏｌ／Ｌ时，Ｋ５６２／Ｄｏｘ对Ｅｐｉ和Ｄａｕ的抗性仍保持５．８和＞６．６倍，很显然这部分抗药性与细胞内药物积聚改变无直接关系，即与Ｐ－ｇｐ过表达无关。

Abstract The purpose of this study was to determine what proportion of drug resistance of MDRcell variant K562 / Dox was attributed to the reduced steady state intracellular drug accumula-tion related to overexpression of P-glycoprotein. K 562 / Dox was derived from repeated expo-sure of human ervthroleukaemic cell line K562 cell to doxorubicin. As assessed with MTTassay, the resistance of K 562/Dox to 7 cytotoxic drugs increased variably in the range between1200 and 11 folds,K562 / Dox cells were positively stained with anti-human p-glycoproteinmonoclonal antibody JSB-1, indicating overexpression of P-gp. Intracellular drug accumula-tion in K562 / Dox,though significantly reduced as compured with that in K562 cells, wasmaximally restored by concurrent exposure of cells to 6 μmol / L verapamil and 1.72 μmol / Leither of the doxorubicin,epirubicin or daunorubicin..Similar results were obtained by exposureof cells to 12 μmol / L verapamil and 8.62 μmol/L drug, indicating that restoration ofintracellular drug accumulation in MDR cells was dependent on the relative concentrations ofverapamil to drug. However,the resistances of K562/Dox cells to epirubicin and daunorubicinstill remained for about 5.6 and > 6.6 folds,respectively, even at verapamil concentration of 6μmol / L, suggesting at least a relatively big fraction of drug resistance was not directly relatedto the altered cellular pharmacokinetics associated with overexpression of P-glycoprotein.