Overexpression of RIP140 suppresses the malignant potential of hepatocellular carcinoma by inhibiting NF­κB­mediated alternative polarization of macrophages.

ABSTRACT

Tumor-associated macrophages (TAMs) and their alternative activation contribute greatly to the development of hepatocellular carcinoma (HCC). Receptor-interacting protein 140 (RIP140) is widely expressed in macrophages and regulates macrophage-mediated energy metabolism, the inflammatory response and tumorigenesis. However, whether RIP140 is involved in the activation of TAMs has not been reported. In the present study, we determined the expression of RIP140 in macrophages after treatment with HCC-conditioned medium (HCM) for 24 h. We also analyzed the effects of RIP140 overexpression on macrophage polarization, invasion and apoptosis of HepG2 and Huh7 cells. Transwell and apoptosis assays were used to estimated cell invasion and apoptosis. In addition, we investigated the effects of RIP140 overexpression in macrophages on the growth of H22 cells by subcutaneous injection of H22 cells along with macrophages in BALB/c nude mice. Western blotting and qRT-PCR were used to detect protein and mRNA expression associated with the NF-κB/IL-6 axis in TAMs. Immunohistochemical and immunofluorescence staining were used to evaluate the protein expression of RIP140 or F4/80 in human HCC samples. The protein expression of RIP140 in peripheral blood mononuclear cells was detected by western blotting. Kaplan­Meier survival curve estimation of overall survival for patients with HCC was based on RIP140 or F4/80 expression in HCC samples. We found that HCM inhibited RIP140 expression and fostered the alternative activation of macrophages. RIP140 overexpression in TAMs significantly inhibited the alternative activation of macrophages by inhibiting the NF-κB/IL-6 axis in TAMs, and suppressed HCC cell growth both in vitro and in vivo. In addition, the protein expression of RIP140 in peripheral blood monocytes was significantly lower in patients with HCC than in healthy people, and this result was consistent with the expression of RIP140 in HCC samples. Furthermore, low RIP140 expression and high F4/80 expression were found to be closely correlated with shorter survival time of the patients with HCC.