MMP9 and hepatocellular carcinoma: In this study, we found that all five genes can be acted as Treg cell-related genes to predict the prognosis and immunotherapy effect of HCC patients, and the expressions of HMOX1, MMP9, and TNFRSF11B were significantly reduced in both Hep3B and Huh7 cells after PD1/PD-L1 inhibitor treatment, suggesting that there is a certain synergy between these genes and anti- PD1/PD-L1 antibodies effect.