PDCD1 and hepatocellular carcinoma: In view of the high abundance of TAMs in tumor tissues and the relevance between antigen presentation by TAMs and immune resistance, reprogramming M2-like TAMs toward M1-like phenotype to ameliorate tumor immunosuppressive microenvironment, present tumor antigen to activate CD8+ T cells and create an APC niche suitable for stem-like CD8+ T cells might be a promising strategy for boosting anti-PD-1 therapy in HCC.