Slapak C A, Martell R L, Terashima M, Levy S B
Center for Adaptation Genetics and Drug Resistance, Tufts University School of Medicine, Boston, MA 02111, USA.
Biochem Pharmacol. 1996 Nov 22;52(10):1569-76. doi: 10.1016/s0006-2952(96)00561-8.
The multidrug resistance protein (MRP) is a membrane protein that mediates altered transport of cytotoxic drugs. Although MRP overexpression has been described in doxorubicin-selected human tumor cell lines, the murine PC-V10 and PC-V40 cell lines are members of the only reported series of vincristine-selected cell lines that overexpress mrp. Western blotting, using an antiserum developed against human MRP, demonstrated high-level expression of murine MRP primarily in the plasma membranes in each of the vincristine-selected cell lines. Only PC-V160, selected for high level resistance, demonstrated concomitant overexpression of the P-glycoprotein. As compared with parental cells, each of the drug-selected cell lines demonstrated an energy-dependent, decreased net accumulation of vincristine without any changes in the initial rates of vincristine influx. However, there was an enhanced rate of vincristine loss, 2.3-fold from the PC-V40 cell line and 3.9-fold from the PC-V160 cell line. Selective plasma membrane permeabilization with digitonin equalized vincristine accumulation among the parental, the PC-V40, and the PC-V160 cell lines. No intracellular pH differences were detected among the cell lines. Despite high-level MRP expression, daunorubicin accumulation and the rate of daunorubicin loss in the PC-V40 cells were the same as that observed in parental PC4 cells. Fluorescence microscopy demonstrated no difference in the pattern of subcellular daunorubicin accumulation between parental and PC-V40 cells. These studies demonstrate that murine MRP, overexpressed and found predominantly in the plasma membrane of vincristine-selected PC-V40 cells, is associated with an energy-dependent increased efflux of vincristine, but not with efflux or altered distribution of daunorubicin.
多药耐药蛋白（MRP）是一种膜蛋白，可介导细胞毒性药物转运的改变。尽管在阿霉素选择的人肿瘤细胞系中已描述了MRP过表达，但鼠PC-V10和PC-V40细胞系是唯一报道的过表达mrp的长春新碱选择细胞系系列的成员。使用针对人MRP产生的抗血清进行的蛋白质印迹显示，在每个长春新碱选择的细胞系中，鼠MRP主要在质膜中高水平表达。仅选择用于高水平抗性的PC-V160显示P-糖蛋白的伴随过表达。与亲本细胞相比，每个药物选择的细胞系均表现出能量依赖性的长春新碱净积累减少，而长春新碱流入的初始速率没有任何变化。然而，长春新碱的损失率有所提高，PC-V40细胞系提高了2.3倍，PC-V160细胞系提高了3.9倍。用洋地黄皂苷进行选择性质膜通透化可使亲本、PC-V40和PC-V160细胞系之间的长春新碱积累达到平衡。在这些细胞系中未检测到细胞内pH差异。尽管MRP高水平表达，但PC-V40细胞中柔红霉素的积累和柔红霉素的损失率与亲本PC4细胞中观察到的相同。荧光显微镜显示亲本细胞和PC-V40细胞之间亚细胞柔红霉素积累模式没有差异。这些研究表明，在长春新碱选择的PC-V40细胞的质膜中过表达并主要发现的鼠MRP与能量依赖性的长春新碱外排增加有关，但与柔红霉素的外排或分布改变无关。
