Gallus Jennifer, Juvale Kapil, Wiese Michael
Pharmaceutical Institute, University of Bonn, Pharmaceutical Chemistry II, An der Immenburg 4, 53121 Bonn, Germany.
Pharmaceutical Institute, University of Bonn, Pharmaceutical Chemistry II, An der Immenburg 4, 53121 Bonn, Germany; Department of Chemistry, Indian Institute of Technology Gandhinagar, Ahmedabad 382424, India.
Biochim Biophys Acta. 2014 Nov;1838(11):2929-38. doi: 10.1016/j.bbamem.2014.08.003. Epub 2014 Aug 13.
Breast Cancer Resistance Protein (BCRP/ABCG2) belongs to the superfamily of ATP binding cassette (ABC) transporters. Characteristic of some of these transporter proteins is the transport of a variety of structurally unrelated substances against a concentration gradient by using the energy of ATP hydrolysis. ABCG2 has been found to confer multidrug resistance (MDR) in cancer cells. Several anticancer drugs have been identified as ABCG2 substrates including mitoxantrone, etoposide and topotecan. As inhibition of the transporter is one of the strategies to overcome MDR, we have synthesized and tested several 3-methoxy flavones and investigated them for their ABCG2 inhibition. Among these, pentamethyl quercetin (compound 4) and pentamethyl morin (compound 5) were found to be fluorescent and hence screened for their possible transport by ABCG2 using confocal microscopy. This study showed that pentamethyl quercetin was far less accumulated in ABCG2 overexpressing MDCK BCRP cells as compared to MDCK sensitive cells, suggesting possible efflux of this compound by ABCG2. Pentamethyl morin showed no visible difference in both cell lines. Based on this observation, we studied several other fluorescent 3-methoxy flavones for their accumulation in ABCG2 overexpressing cells. To confirm the substrate or inhibitor nature of the tested compounds, these compounds were further investigated by ATPase assay. If stimulation of the transporter ATPase activity is detected, one can conclude that the compound is probably a transported substrate. All compounds except pentamethyl morin (compound 5) and tetramethyl quercetin (compound 6) were found to stimulate ATPase activity pointing to possible substrates despite being potent inhibitors of ABCG2.
乳腺癌耐药蛋白（BCRP/ABCG2）属于ATP结合盒（ABC）转运蛋白超家族。这些转运蛋白中的一些具有的特点是利用ATP水解产生的能量逆浓度梯度转运多种结构不相关的物质。已发现ABCG2赋予癌细胞多药耐药性（MDR）。几种抗癌药物已被确定为ABCG2底物，包括米托蒽醌、依托泊苷和拓扑替康。由于抑制该转运蛋白是克服MDR的策略之一，我们合成并测试了几种3-甲氧基黄酮，并研究了它们对ABCG2的抑制作用。其中，五甲基槲皮素（化合物4）和五甲基桑色素（化合物5）具有荧光，因此使用共聚焦显微镜筛选它们是否可能被ABCG2转运。这项研究表明，与MDCK敏感细胞相比，五甲基槲皮素在过表达ABCG2的MDCK BCRP细胞中的积累要少得多，这表明该化合物可能被ABCG2外排。五甲基桑色素在两种细胞系中均未显示出明显差异。基于这一观察结果，我们研究了其他几种荧光3-甲氧基黄酮在过表达ABCG2的细胞中的积累情况。为了确认测试化合物的底物或抑制剂性质，通过ATP酶测定对这些化合物进行了进一步研究。如果检测到转运蛋白ATP酶活性受到刺激，则可以得出该化合物可能是转运底物的结论。除五甲基桑色素（化合物5）和四甲基槲皮素（化合物6）外，所有化合物均被发现可刺激ATP酶活性，这表明尽管它们是ABCG2的强效抑制剂，但可能是底物。
