Mülder H S, Dekker H, Pinedo H M, Lankelma J
University Hospital Vrije Universiteit, Department of Medical Oncology, Amsterdam, The Netherlands.
Biochem Pharmacol. 1995 Sep 28;50(7):967-74. doi: 10.1016/0006-2952(95)00221-k.
We have used a new methodology to measure the activity of P-glycoprotein (P-gp) in multidrug-resistant (MDR) tumor cells. This activity leads to a lower cytosolic concentration and a lower cytotoxicity of the classical anthracyclines, daunorubicin (DNR), and doxorubicin (DOX). It has been reported that the anthracycline idarubicin (IDA), which is more lipophilic, has a higher clinical efficacy in acute myeloid leukemias (AML) than DNR and DOX. In our study, the aim was to determine for a series of anthracyclines how variations in the passive drug influx rate as well as the P-gp-mediated drug pumping rate affect their cytosolic free drug concentrations and how these parameters are related to drug cytotoxicity. We selected six anthracyclines: DOX, DNR, epidoxorubicin (EPI), IDA, cyano-morpholino-doxorubicin (CMD), and carminomycin (CAR), ordered according to their increasing octanol/PBS buffer concentration ratios, respectively. To measure the passive permeation coefficient, the P-gp-mediated drug pumping rate, and the cytosolic free drug concentration, we used a flow-through system in which cells were exposed to a flowing medium containing drugs. We used the MDR P-gp-containing cell line KB8-5. It was shown that the passive drug permeation coefficient as well as the drug pumping rate of P-gp increased with increasing lipophilicity in this series of anthracyclines. The cytosolic free drug concentration was lowered by P-gp to a similar extent in KB8-5 cells for all drugs tested (40-50% of the extracellular drug concentration). CMD, IDA, and CAR had lower IC50 values and lower resistance factors in comparison to DOX, DNR, and EPI. Verapamil reversed the resistance for all anthracyclines tested. In conclusion, for several anthracyclines the activity of P-gp leads to a similar relative decrease in the cytosolic free drug concentration; consequently, the reported lower resistance factor of IDA compared to that of DNR is not due to the inability of P-gp to export IDA from cells.
我们采用了一种新方法来测量多药耐药（MDR）肿瘤细胞中P-糖蛋白（P-gp）的活性。这种活性导致经典蒽环类药物柔红霉素（DNR）和阿霉素（DOX）的胞质浓度降低和细胞毒性降低。据报道，亲脂性更强的蒽环类药物伊达比星（IDA）在急性髓系白血病（AML）中的临床疗效高于DNR和DOX。在我们的研究中，目的是确定一系列蒽环类药物的被动药物流入速率以及P-gp介导的药物泵出速率的变化如何影响其胞质游离药物浓度，以及这些参数与药物细胞毒性有何关系。我们选择了六种蒽环类药物：DOX、DNR、表柔比星（EPI）、IDA、氰基吗啉多柔比星（CMD）和卡米诺霉素（CAR），分别按照它们不断增加的辛醇/磷酸盐缓冲盐水浓度比排序。为了测量被动渗透系数、P-gp介导的药物泵出速率和胞质游离药物浓度，我们使用了一种流通系统，在该系统中细胞暴露于含有药物的流动介质中。我们使用了含有MDR P-gp的细胞系KB8-5。结果表明，在这一系列蒽环类药物中，被动药物渗透系数以及P-gp的药物泵出速率随着亲脂性的增加而增加。在KB8-5细胞中，对于所有测试药物，P-gp将胞质游离药物浓度降低到相似程度（细胞外药物浓度的40-50%）。与DOX、DNR和EPI相比，CMD、IDA和CAR具有更低的IC50值和更低的耐药因子。维拉帕米逆转了所有测试蒽环类药物的耐药性。总之，对于几种蒽环类药物，P-gp的活性导致胞质游离药物浓度出现相似的相对降低；因此，与DNR相比，报道的IDA较低的耐药因子并非由于P-gp无法将IDA从细胞中输出。
