Ginsenoside Rg3 Decreases NHE1 Expression via Inhibiting EGF-EGFR-ERK1/2-HIF-1 α Pathway in Hepatocellular Carcinoma: A Novel Antitumor Mechanism

Abstract

Na ${}^{+}$ /H ${}^{+}$ exchanger 1 (NHE1) plays a vital role in the oncogenesis and development of hepatocellular carcinoma (HCC) and has been regarded as a promising target for the treatment of HCC. Ginsenoside Rg3 (Rg3), a bioactive ginseng compound, is suggested to possess pleiotropic antitumor effects on HCC. However, the underlying mechanisms of Rg3 suppressing HCC remain unclear. In the present study, we uncovered a novel antitumor mechanism of Rg3 on HCC by decreasing NHE1 expression through in vivo and in vitro studies. Mechanistically, we demonstrated that epidermal growth factor (EGF) could dramatically upregulate NHE1 expression, while increasing the phosphorylated extracellular signal-regulated protein kinase (ERK1/2) level and hypoxia-inducible factor 1 alpha (HIF-1 $\alpha )$ expression. In the presence of ERK1/2-specific inhibitor PD98059, EGF stimulated HIF-1 $\alpha$ and NHE1 expression was obviously blocked in addition, the presence of HIF-1 $\alpha$ -specific inhibitor 2-methoxyestradiol (2-MeOE2) blocked EGF stimulated NHE1 expression. Moreover, results from in vivo and in vitro studies indicate that Rg3 treatment markedly decreased the expression of EGF, EGF receptor (EGFR), phosphorylated ERK1/2 and HIF-1 $\alpha$ . Conclusively, these findings suggested that NHE1 was stimulated by EGF, and Rg3 could decrease NHE1 expression by integrally inhibiting EGF-EGFR-ERK1/2-HIF- $\alpha$ signal axis in HCC. Together, our evidence indicated that Rg3 was an effective multi-targets antitumor agent for the treatment of HCC.

Keywords: EGF; Ginsenoside Rg3; HIF-1$\alpha$; Hepatocellular Carcinoma; NHE1.