CD274 and hepatocellular carcinoma: TT-LDCP NPs contain siRNAs targeting the immune checkpoint ligand PD-L1 and plasmid DNA encoding the immunostimulatory factor IL-2, which can work together to inhibit immune-suppressive signals while enhancing immune-activating signals [173,174], which promotes tumor infiltration and CD8+ T-cell activation [175,176], and effectively curbs the progression of HCC.