Long-term use of indomethacin leads to poor prognoses through promoting the expression of PD-1 and PD-L2 via TRIF/NF-κB pathway and JAK/STAT3 pathway to inhibit TNF-α and IFN-γ in hepatocellular carcinoma

• Long-term use of indomethacin inhibits TNF-α and IFN-γ in vivo and in vitro.
• Long-term use of indomethacin promoted the expression of PD-1 and PD-L2.
• Using indomethacin for long activates TRIF/NF-κB and JAK/STAT3 pathways in γδ T cells.

HCC still has a poor prognosis in clinical due to high recurrence and metastasis rates worldwide nowadays. Indomethacin pretreatment is used as a potential chemopreventive agent in cancers for it could assist in anti-tumor functions of other agents and exert anti-tumor effect. Our study aims to discuss the effects and mechanisms of long-term use of indomethacin in HCC. The HepA mouse models were used to observe tumor recurrence, intrahepatic metastasis and remote metastasis. NK cell, αβ T cell and γδ T cell were used to explore the underlying mechanisms for anti-tumor effect of indomethacin. The results showed that long-term use of indomethacin facilitated intrahepatic recurrence, intrahepatic dissemination and lung metastasis, and indomethacin inhibits TNF-α and IFN-γ in vivo and in vitro in a dose-dependent manner. Furthermore, long-term use of indomethacin increased the expression of PD-1 and PD-L2 in programmed death-1 pathway. Blockade of PD-1 and PD-L2 reversed the reduced production of TNF-α and IFN-γ induced by indomethacin in γδ T cells. In addition, long-term use of indomethacin activates TRIF/NF-κB and JAK/STAT3 pathways, and indomethacin promotes the expression of PD-1 and PD-L2 via TRIF/NF-κB pathway and JAK/STAT3 pathway respectively in γδ T cells. Given these findings, we drew a conclusion that long-term use of indomethacin leads to poor prognoses through promoting the expression of PD-1 and PD-L2 via TRIF/NF-κB pathway and JAK/STAT3 pathway to inhibit TNF-α and IFN-γ in HCC.