Division of Molecular Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
Mol Pharm. 2011 Apr 4;8(2):571-82. doi: 10.1021/mp1003898. Epub 2011 Mar 4.
P-glycoprotein (P-gp/ABCB1) and breast cancer resistance protein (BCRP/ABCG2) combination knockout mice display disproportionately increased brain penetration of shared substrates, including topotecan and several tyrosine kinase inhibitors, compared to mice deficient for only one transporter. To better study the interplay of both transporters also in vitro, we generated a transduced polarized MDCKII cell line stably coexpressing substantial levels of human ABCB1 and ABCG2 (MDCKII-ABCB1/ABCG2). Next, we measured concentration-dependent transepithelial transport of topotecan, sorafenib and sunitinib. By blocking either one or both of the transporters simultaneously, using specific inhibitors, we aimed to mimic the ABCB1-ABCG2 interplay at the blood-brain barrier in wild-type, single or combination knockout mice. ABCB1 and ABCG2 contributed to similar extents to topotecan transport, which was only partly saturable. For sorafenib transport, ABCG2 was the major determinant at low concentrations. However, saturation of ABCG2-mediated transport occurred at higher sorafenib concentrations, where ABCB1 was still fully active. Furthermore, sunitinib was transported equally by ABCB1 and ABCG2 at low concentrations, but ABCG2-mediated transport became saturated at lower concentrations than ABCB1-mediated transport. The relative impact of these transporters can thus be affected by the applied drug concentrations. A comparison of the in vitro observed (inverse) transport ratios and cellular accumulation of the drugs at low concentrations with in vivo brain penetration data from corresponding Abcb1a/1b⁻/⁻, Abcg2⁻/⁻ and Abcb1a/1b;Abcg2⁻/⁻ mouse strains revealed very similar qualitative patterns for each of the tested drugs. MDCKII-ABCB1/ABCG2 cells thus present a useful in vitro model to study the interplay of ABCB1 and ABCG2.
P-糖蛋白（P-gp/ABCB1）和乳腺癌耐药蛋白（BCRP/ABCG2）双敲除小鼠与仅一种转运体缺乏的小鼠相比，其共同底物包括拓扑替康和几种酪氨酸激酶抑制剂在内的脑内穿透率显著增加。为了更好地在体外研究两种转运体的相互作用，我们生成了稳定共表达大量人 ABCB1 和 ABCG2 的转导极化 MDCKII 细胞系（MDCKII-ABCB1/ABCG2）。接下来，我们测量了拓扑替康、索拉非尼和舒尼替尼的浓度依赖性跨上皮转运。通过使用特定抑制剂同时阻断一种或两种转运体，我们旨在模拟野生型、单敲除或双敲除小鼠血脑屏障中 ABCB1-ABCG2 的相互作用。ABCB1 和 ABCG2 对拓扑替康转运的贡献相似，且只有部分达到饱和。对于索拉非尼转运，ABCG2 是低浓度下的主要决定因素。然而，当达到较高的索拉非尼浓度时，ABCG2 介导的转运达到饱和，此时 ABCB1 仍完全活跃。此外，在低浓度下，舒尼替尼同样由 ABCB1 和 ABCG2 转运，但 ABCG2 介导的转运在低于 ABCB1 介导的转运的浓度下达到饱和。因此，这些转运体的相对影响可能受应用药物浓度的影响。将在低浓度下观察到的（逆）转运比和药物的细胞积累与相应的 Abcb1a/1b⁻/⁻、Abcg2⁻/⁻ 和 Abcb1a/1b;Abcg2⁻/⁻ 小鼠品系的体内脑穿透数据进行比较，结果表明，每种测试药物的定性模式非常相似。因此，MDCKII-ABCB1/ABCG2 细胞是研究 ABCB1 和 ABCG2 相互作用的有用体外模型。
