The functional roles of immune cells in primary liver cancer

Primary liver cancer includes hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA). Incidence of liver cancer has been increasing in recent years, and the 5-year survival is <20%. HCC and CCA are often accompanied with a dense stroma coupled with infiltrated immune cells, which is referred to as the tumor microenvironment. Populations of specific immune cells, such as high density of CD163+ macrophages and low density of CD8+ T cells, are associated with prognosis and survival rates in both HCC and CCA. Immune cells in the tumor microenvironment can be a therapeutic target for liver cancer treatments. Previous studies have introduced immunotherapy using immune checkpoint inhibitors, pulsed dendritic cells, or transduced T cells, to enhance cytotoxicity of immune cells and inhibit tumor growth. This review summarizes current understanding of the roles of immune cells in primary liver cancer covering HCC and CCA. (Am J Pathol 2022, 192: 826-836; https://doi.org/10.1016/ j.ajpath.2022.02.004)