The combination of PD-1 blockade with interferon-α has a synergistic effect on hepatocellular carcinoma

The efficacy of immune checkpoint inhibitors (ICIs), such as programmed cell death protein-1 (PD-1) or its ligand 1 (PD-L1) antibody, in hepatocellular carcinoma (HCC) is limited, and it is recommended that they be combined with other therapies. We evaluated the combination of pegylated interferon-α (Peg-IFNα) with PD-1 blockade in HCC mouse models. We analyzed the effects of Peg-IFNα on tumor-infiltrating immune cells and PD-1 expression in the HCC immune microenvironment and examined the underlying mechanism of its unique effect on the PD-1 pathway. The in vivo efficacy of anti-PD-1 and Peg-IFNα was evaluated in both subcutaneous and orthotopic mouse models of HCC. The combination of Peg-IFNα with PD-1 blockade dramatically enhanced T-cell infiltration, improved the efficacy of PD-1 antibody and prolonged mouse survival compared with PD-1 antibody monotherapy. Mechanistically, Peg-IFNα could recruit cytotoxic CD8+ T cells to infiltrate the HCC microenvironment by inducing tumor cells to secrete the chemokine CCL4. Nevertheless, the HCC microenvironment quickly overcame the immune responses by upregulating PD-1 expression in CD8+ T cells via the IFNα-IFNAR1-JAK1-STAT3 signaling pathway. The combination of PD-1 blockade with Peg-IFNα could restore the cytotoxic capacity of CD8+ T cells and exerted a significant synergistic effect on HCC. These results indicate that in addition to initiating the antitumor immune response itself, Peg-IFNα can also generate a microenvironment favoring PD-1 blockade. Thus, the combination of Peg-IFNα and PD-1 blockade can be a promising strategy for HCC.