IDO1 and hepatocellular carcinoma: In this study, we found a positive correlation between interferon-γ (IFN-γ) and PD-L1 in HCC cells (Figure 1B), and this study found that Abrine could decrease the PD-L1 expression in IFN-γ, PBMCs, and IDO1-induced IDO1 overexpression HepG2 cells (Figures 5A–C).