Targeting Na+/K+-ATPase by berbamine and ouabain synergizes with sorafenib to inhibit hepatocellular carcinoma

Background and Purpose The multikinase inhibitor sorafenib is a first-line drug for advanced hepatocellular carcinoma. The response to sorafenib varies among hepatocellular carcinoma patients and many of the responders suffer from reduced sensitivity after long-term treatment. This study aims to explore a novel strategy to potentiate or maximize the anti-hepatocellular carcinoma effects of sorafenib. Experimental Approach We used hepatocellular carcinoma cell lines, western blotting, various antagonists, siRNA and tumour xenografts mouse model to determine the anti- hepatocellular carcinoma effects of sorafenib in combination with berbamine or other Na+/K+-ATPase ligands. Key Results Berbamine and the cardiotonic steroid, ouabain, synergize with sorafenib to inhibit hepatocellular carcinoma cells growth. Mechanistically, berbamine induces Src phosphorylation in Na+/K+-ATPase-dependent manner, leading to the activation of p38MAPK and EGFR-ERK pathways. The Na+/K+-ATPase ligand ouabain also induces Src, EGFR, type I insulin-like growth factor receptor, ERK1/2 and p38MAPK phosphorylation in hepatocellular carcinoma cells. Treatment of hepatocellular carcinoma cells with Src or EGFR inhibitor inhibits the induction of ERK1/2 phosphorylation by berbamine. Moreover, sorafenib inhibits the induction of Src, p38MAPK, EGFR and ERK1/2 phosphorylation by berbamine and ouabain. Importantly, combination of sorafenib with berbamine or ouabain synergistically inhibits both sorafenib-naive and sorafenib-resistant hepatocellular carcinoma cells growth. Co-treatment of hepatocellular carcinoma cells with berbamine and sorafenib significantly induces cell death and significantly inhibits hepatocellular carcinoma xenografts growth in vivo. Conclusion and Implications Berbamine or other Na+/K+-ATPase ligands have a potential for improving sorafenib responsiveness in hepatocellular carcinoma. Targeting Na+/K+-ATPase represents a novel strategy to potentiate the anti- hepatocellular carcinoma effects of sorafenib.