Satonaka Hana, Ishida Kumiki, Takai Miho, Koide Ryoji, Shigemasa Ryota, Ueyama Jun, Ishikawa Tetsuya, Hayashi Kazuhiko, Goto Hidemi, Wakusawa Shinya
Division of Medical Laboratory Sciences, Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Japan.
Division of Gastroenterology, Department of Internal Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan.
Anticancer Res. 2017 Nov;37(11):6071-6077. doi: 10.21873/anticanres.12055.
BACKGROUND/AIM: (-)-Epigallocatechin-3-gallate (EGCG) has been indicated to regulate the function of P-glycoprotein (P-gp), which is a drug transporter encoded by the MDR1 (ABCB1) gene. P-gp expression is induced by doxorubicin (DOX). We aimed to clarify the mechanisms and inhibitory effects of EGCG on DOX-induced P-gp expression in HepG2 cells.
Rhodamine 123 (Rho123) was used for P-gp substrate. Western blotting and polymerase chain reactions (PCRs) were conducted using specific antibodies and primer sets.
The DOX-pretreated cells accumulated a significantly decreased amount of Rho123), than control cells; however, the cells pretreated with EGCG and DOX, in combination, accumulated Rho123 more than DOX-pretreated cells. DOX induced the overexpression of MDR1 mRNA and increased the phosphorylation of Akt, ERK1/2, p38 MAPK and JNK. EGCG significantly inhibited the phosphorylation of Akt and ERK. The DOX-induced P-gp overexpression was partially suppressed by an inhibitor of MEK1/2 (U0126), but not by a PI3K inhibitor (LY294002). Interestingly, the expression of P-gp was synergistically inhibited by combined treatment of U0126 with LY294002 and also inhibited by an mTORC1 inhibitor, rapamycin.
EGCG inhibited DOX-induced overexpression of P-gp through the coordinate inhibitory action on MEK/ERK and PI3K/Akt signaling pathways.
背景/目的：（-）-表没食子儿茶素-3-没食子酸酯（EGCG）已被证实可调节P-糖蛋白（P-gp）的功能，P-糖蛋白是一种由MDR1（ABCB1）基因编码的药物转运蛋白。阿霉素（DOX）可诱导P-gp表达。我们旨在阐明EGCG对DOX诱导的HepG2细胞中P-gp表达的作用机制及抑制作用。
罗丹明123（Rho123）用作P-gp底物。使用特异性抗体和引物对进行蛋白质免疫印迹法和聚合酶链反应（PCR）。
DOX预处理的细胞中Rho123的积累量明显低于对照细胞；然而，EGCG和DOX联合预处理的细胞比DOX预处理的细胞积累更多的Rho123。DOX诱导MDR1 mRNA的过表达，并增加Akt、ERK1/2、p38 MAPK和JNK的磷酸化。EGCG显著抑制Akt和ERK的磷酸化。MEK1/2抑制剂（U0126）可部分抑制DOX诱导的P-gp过表达，但PI3K抑制剂（LY294002）则无此作用。有趣的是，U0126与LY294002联合处理可协同抑制P-gp的表达，mTORC1抑制剂雷帕霉素也可抑制其表达。
EGCG通过对MEK/ERK和PI3K/Akt信号通路的协同抑制作用，抑制DOX诱导的P-gp过表达。
