Methotrexate cross-resistance in a mitoxantrone-selected multidrug-resistant MCF7 breast cancer cell line is attributable to enhanced energy-dependent drug efflux.
Methotrexate cross-resistance in a mitoxantrone-selected multidrug-resistant MCF7 breast cancer cell line is attributable to enhanced energy-dependent drug efflux.
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发表时间：
2000-07
期刊：
影响因子：
11.2
通讯作者：
E. L. Volk;Kristin Rohde;M. Rhee;J. McGuire;L. Doyle;Douglas D. Ross;E. Schneider
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文献类型：
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作者：
E. L. Volk;Kristin Rohde;M. Rhee;J. McGuire;L. Doyle;Douglas D. Ross;E. Schneider
细胞对抗叶酸甲氨蝶呤 (MTX) 的耐药性通常是由靶点扩增、摄取缺陷或多谷氨酰化的改变引起的。在这里，我们检查了在米托蒽醌存在下选择的人乳腺癌细胞系 (MCF7/MX) 中的 MTX 交叉耐药性，米托蒽醌是一种与多药耐药 (MDR) 表型相关的抗癌药物。蛋白质表达和酶活性的检查表明MCF7/MX细胞没有表现出任何MTX耐药的经典机制。然而，它们确实表现出 ATP 敏感的积累缺陷，并伴有多谷氨酰化减少。尽管亲本细胞和耐药细胞之间的药物摄取动力学相似，但耐药细胞表现出能量依赖性药物流出增加。这表明 ATP 结合盒 (ABC) 转运蛋白的参与。然而，用乳腺癌抗性蛋白(BCRP)转染的细胞——ABC转运蛋白已知在MCF7/MX细胞中高度过表达并赋予米托蒽醌抗性(D.D.Ross等人，J.Natl.Cancer Inst.91：429-433，1999)——不具有MTX抗性，这表明该转运蛋白不参与MTX交叉抗性。此外，先前与 MTX 抗性有关的转运蛋白 MRP 蛋白家族的成员并未发现在 MCF7/MX 细胞中过度表达。因此，我们的数据表明，一种新型的 MTX 特异性外排泵可能与这种不寻常的交叉耐药表型有关。
Cellular resistance to the antifolate methotrexate (MTX) is often caused by target amplification, uptake defects, or alterations in polyglutamylation. Here we have examined MTX cross-resistance in a human breast carcinoma cell line (MCF7/MX) selected in the presence of mitoxantrone, an anticancer agent associated with the multidrug resistance (MDR) phenotype. Examination of protein expression and enzyme activities showed that MCF7/MX cells displayed none of the classical mechanisms of MTX resistance. They did, however, exhibit an ATP-sensitive accumulation defect accompanied by reduced polyglutamylation. Although the kinetics of drug uptake was similar between parental and resistant cells, the resistant cells exhibited increased energy-dependent drug efflux. This suggested the involvement of an ATP-binding cassette (ABC) transporter. However, cells transfected with the breast cancer resistance protein (BCRP)-the ABC transporter known to be highly overexpressed in MCF7/MX cells and to confer mitoxantrone resistance (D. D. Ross et al., J. Natl. Cancer Inst. 91: 429-433, 1999)-were not MTX resistant, which suggested that this transporter is not involved in MTX cross-resistance. Moreover, members of the MRP protein family of transport proteins, which had previously been implicated in MTX resistance, were not found to be overexpressed in the MCF7/MX cells. Thus, our data suggest that a novel MTX-specific efflux pump may be involved in this unusual cross-resistance phenotype.