CTLA4 and neoplasm: Moreover, overexpression of immune checkpoints (cell death protein 1 (PD-1), and its ligand) on hepatocytes, hepatic stellate cells, KC, LSEC, and intrahepatic leukocytes [20] and the activation of cytotoxic T-cell-associated protein 4 (CTLA-4) on the surface of T regulatory cells (Treg) [21] appears to further contribute to tumor progression.