TLR3 activation enhances sorafenib-antitumor effect in hepatocellular carcinoma by activating NK cell functions through ERK and NF-κB pathways

Abstract Background: Sorafenib is a standard therapeutic agent for advanced hepatocellular carcinoma (HCC). But its efficacy is moderate because the survival of patients is only extended by a few months, and the response rate is low and the mechanism of low efficacy is unclear. In this study, we investigated the effect of TLR3 on sorafenib against HCC. Methods: Polyinosinic: polycytidylic acid [Poly(I:C)] functioned as a dsRNA analog and TLR3 agonist, which was employed in following experiments. The HCC tumor was orthotopically implanted into in BALBc nu/nu or C57BL/6 mice. We analyzed survival times of mice, along with tumor growth, metastasis within abdoman and to lung. Flow cytometry and cytotoxicity assay were used to analyze the NK cells which was isolated from spleen or peripheral blood. ELISA assay was used to detect the expression of plasma interferon (IFN)-γ and monocyte chemoattractant protein (MCP)-1. Furthermore, the expression of pERK1/2, pAKT, ERK1/2 and AKT was analyzed by Western blot. Results: Sorafenib reduced the number and activities of NK cells in tumor-bearing mice concomitant with decreased plasma levels of MCP-1 and IFN-γ. The combination of sorafenib and Poly(I:C) synergistically inhibited tumor growth and metastasis in tumor xenograft mouse, and thus prolonged mice survival. Poly(I:C) not only exerted a direct inhibitory effect on tumor growth and metastasis by targeting the TLR3 receptor on tumor cells but also facilitated NK cell proliferation and activation, indirectly impeding tumor progression. Mechanistically, Poly(I:C) decreased sorafenib-induced inhibition of ERK phosphorylation, increased IκB phosphorylation in NK cells, and enhanced NK cell function. Conclusion: Activation of TLR3 could enhance sorafenib-antitumor effect in HCC. The combination of TLR3 activator and sorafenib could be a new strategy for HCC treatment.