LAUSR

Background Hepatocellular carcinoma (HCC) has become the sixth most common cancer and the third leading cause of cancer death in the world. Although the research achievements of tumor immunotherapy have made great progress, especially the combination of immune targeted therapy has achieved good curative effect in HCC, but only a few patients are suitable for it and benefit from it. Therefore, there is an urgent need to find new effective drugs to treat HCC or to enhance the sensitivity of immunotherapy. Methods Meloxicam, a COX2 inhibitor with strong anti-HCC potential, was screened from 800 small molecules approved by FDA. The effect of meloxicam on the proliferation, invasion, and migration of HCC cell lines was evaluated by cell phenotype analysis. The Human Protein Atlas database and the TISCH database were used to analyze COX2 data in single cells, and the TISIDB database was used to analyze the correlation of COX2 with immune function. The real-time quantitative polymerase chain reaction (qRT-PCR) and western blot were used to evaluate the level of PD-L1 and CD155 in HCC cell lines treated with meloxicam and further explore its possible mechanism. In vivo experiments were applied to verify the effect of meloxicam combined with anti-PD1 therapy on HCC tumor growth in mice. Results Meloxicam can significantly inhibit the proliferation, invasion, and migration of HCC cells. The TISIDB database indicated that the COX2 was strongly associated with immunoinhibitors and immunostimulators. Meloxicam upregulated the level of PD-L1 in HCC cell lines and animal models. In terms of mechanism, meloxicam inhibited microRNA-200, thereby upregulating PD-L1. In vitro experiments showed that both meloxicam and anti-PD1 had inhibitory effects on the growth of HCC tumors. Compared with meloxicam and anti-PD1 alone, the combination therapy showed stronger antitumor properties. Immunohistochemical analysis confirmed that meloxicam enhanced the antitumor immune activity in the tumor microenvironment. Conclusion Our study showed meloxicam inhibited HCC progression and enhanced the sensitivity of immunotherapy via the microRNA-200/PD-L1 pathway.