IDO1 and central nervous system cancer: Other immune checkpoints or immune-related molecules implicated in glioma include lymphocyte activation gene 3 (LAG-3), ecto-5’-nucleotidase/cluster of differentiation 73 (CD73), cluster of differentiation 161 (CD161), hepatitis A virus cellular receptor 2 (HAVCR2), indoleamine 2,3-dioxygenase 1 (IDO1), V-domain immunoglobulin suppressor of T cell activation (VISTA), V-set domain containing T cell activation inhibitor 1 (VTCN1), CD27/CD70, B, and T lymphocyte attenuator (BTLA), cluster of differentiation 39 (CD39), CD276, cluster of differentiation 47 (CD47), and many others.