A20 Inhibits IFN-γ Signaling in Hepatocellular Carcinoma Cells by Binding to STAT1, Compromising Anti-Tumor Immunity.

Immune checkpoint blockade (ICB) has demonstrated efficacy in clinical cancer therapy; however, a significant proportion of cancer patients do not respond to ICB. One contributing factor to this lack of response is the impairment of IFN-γ signaling within cancer cells. A20 acts as a negative regulator of IFN-γ signaling. Our study aimed to investigate the mechanism by which A20 exerts its negative regulatory effect on IFN-γ signaling in hepatocellular carcinoma (HCC) cells. Bioinformatic analysis revealed that A20 expression in HCC cell lines is inversely associated with the activation of IFN-γ signaling. Functional loss and gain experiments demonstrated that A20 inhibits IFN-γ signaling in HCC cells. The interaction between A20 and STAT1 was assessed using Co-Immunoprecipitation (Co-IP) assays and bimolecular fluorescence complementation (BioFC) assays. Our results also indicated that A20 suppresses the expression of downstream molecules involved in IFN-γ signaling, such as CXCL9, CXCL10, and HLA-ABC, in HCC cells. Additionally, enforced expression of A20 in HCC cells inhibited anti-tumor immunity in a mouse model of HCC. Bioinformatic analysis suggests that A20 may negatively regulate IFN-γ signaling in HCC cells from human HCC cohorts. Collectively, our study uncovers a novel mechanism whereby A20 inhibits IFN-γ signaling in HCC cells through direct binding with STAT1. These findings enhance our understanding of the regulatory mechanisms of IFN-γ signaling in cancer cells and provide insights for designing strategies to enhance the effectiveness of ICB therapy.