(–)-Epigallocatechin-3-gallate Down-regulates Doxorubicin-induced Overexpression of P-glycoprotein Τhrough the Coordinate Inhibition of PI3K/Akt and MEK/ERK Signaling Pathways

Abstract

Abstract. Background/Aim: (-)-Epigallocatechin-3-gallate (EGCG) has been indicated to regulate the function of Pglycoprotein (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. Materials and Methods: Rhodamine 123 (Rho123) was used for P-gp substrate. Western blotting and polymerase chain reactions (PCRs) were conducted using specific antibodies and primer sets. Results: The DOXpretreated 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. Conclusion: EGCG inhibited DOX-induced overexpression of P-gp through the coordinate inhibitory action on MEK/ERK and PI3K/Akt signaling pathways.(-)-Epigallocatechin gallate (EGCG) is the most abundant component of tea polyphenols having various profitable properties, including anti-oxidative activity and cancerpreventive effect (1). In addition, concerning antitumor drug resistance, EGCG has been shown to decrease doxorubicin (DOX) resistance in a human carcinoma xenograft model mice (2) and inhibit the transport function of P-glycoprotein (P-gp), an export drug transporter causing antitumor multidrug resistance (MDR) in tumor cells (3)(4)(5).Human P-gp is a plasma membrane protein of 170 kDa encoded by the MDR1 (ABCB1) gene. The expression of MDR1 gene and P-gp is affected by various chemical substances and physico-chemical stress (5-7). We have previously suggested that the P-gp level was up-regulated through the activation of protein kinase C/nuclear factor-ĸB (PKC/NF-ĸB) in rats with streptozotocin-induced diabetes (8). Further, the expression of MDR1 gene has been also shown to be induced by PI3K/Akt/NF-ĸB signaling (9,10).EGCG has been shown to activate ERK and PI3K/Akt signaling and induce antioxidant enzymes in human mammary epithelial cells (11). Contrarily, it has been shown that EGCG inhibits the PI3K/Akt system in fibroblast cells (12) and the phosphorylation of ERK and Akt kinases in epidermal growth factor (EGF)-stimulated cells (13). More recently, accumulating evidence indicates that EGCG can inhibit PI3K/Akt and MAPK signaling systems (14)(15)(16)(17).From these backgrounds, in the present study, we aimed to clarify whether EGCG could suppress MDR and inhibit the induction of P-gp overexpression by DOX through inhibition of PI3K/Akt and ERK/MAPK signal transduction s...

Epigallocatechin-3-gallate confers protection against corticosterone-induced neuron injuries via restoring extracellular signal-regulated kinase 1/2 and phosphatidylinositol-3 kinase/protein kinase B signaling pathways

“…Mechanistically, EGCG pre-treatment significantly attenuated the corticosterone-mediated inhibition of ERK1/2 and PI3K/AKT phosphorylation, which are critical merging points for many signaling cascades involved in the regulation of cell survival, cell growth and proliferation under physiological and pathophysiologic conditions [ 41 , 42 ]. EGCG has been shown to modulate ERK and PI3K/AKT signaling systems in different tissues and cell lines [ 1 , 4 , 43 – 45 ]. In the nervous system, a low level of ERK activation is needed to promote neuronal growth, thereby facilitating neuronal plasticity and survival [ 46 ].…”

<p>Epigallocatechin-3-gallate in the prevention and treatment of hepatocellular carcinoma: experimental findings and translational perspectives</p>

“…Moreover, EGCG enhanced the inhibitory effects of sorafenib on anaerobic HCC-cell growth and in an HCC-xenograft mouse model. Recently, it has been shown that EGCG attenuates the overexpression of Pgp induced by Dox in HepG2 cells by inhibiting the ERK–MAPK and PI3K–Akt signaling pathways 62. Finally, a new molecular mechanism underlying the EGCG-mediated autophagic modulation of AFP in HepG2 cells has been proposed by Zhao et al63 Taken together, all these findings suggest that EGCG could be conceivably utilized for counteracting and treating HCC by acting on different molecular mechanisms.…”

“…In the CAMARADES analysis (Table 3), we found that all the studies considered were published in peer-reviewed journals and showed detailed biochemical/tissue evaluations and professional statistical analysis. The newest studies8,62 obtained the highest score (9/11) despite the lack of any allocation-concealment technique, mandatory to prevent selection bias. This criterion is often underestimated, as demonstrated in our previous CAMARADES evaluations 64.…”

“…EGCG-induced inhibition of vascular invasion was also studied by Darweish et al8 In an animal model of HCC, the authors demonstrated that EGCG was able to induce restoration of HSPG receptors. In a murine xenograft model of HCC, Li et al62 demonstrated that EGCG inhibited glycolysis and induced apoptosis in HCC cells through inhibition of the expression and activity of PFK, a limiting enzyme of glycolysis. As a consequence of this effect, EGCG improved the resistance of aerobic glycolytic HCC cells to sorafenib and enhanced cell-growth inhibition.…”

Attenuation of everolimus-induced cytotoxicity by a protective autophagic pathway involving ERK activation in renal cell carcinoma cells

“…Particularly, cross talk between these two pathways has been well illustrated in previous studies. 15 – 17 Moreover, several studies have shown that inhibition of the ERK pathway enhanced the antitumor activity of RAD001 in pediatric gliomas, 18 neuroblastoma, 19 and acute myelogenous leukemia. 20 Thus, the aim of this study was to identify the underlying mechanisms and biochemical pathways involved in RAD001 resistance in RCC.…”