VTCN1 and hepatocellular carcinoma: B7 superfamily member 1 (B7S1/B7-H4/B7x/VTCN1) nullifies CD8+ T cell functions, and the expression of this molecule on myeloid cells in HCC is elevated, shows a positive correlation with CD8+ T cell dysfunction and promotes T lymphocyte depletion and co-expression with PD-1, which suggests a synergistic relationship between these two proteins [190].