IDO1 and neoplasm: Interestingly, RNA-Seq analysis showed that approximately half of the UM tumors displayed an increased expression of immunomodulatory molecules related to T-cell suppression, such as galectin 3, programmed death-ligand 1, cytotoxic T-lymphocyte-associated protein 4, indoleamine 2,3-dioxygenase 1, and lymphocyte activating 3, potentially explaining why T cells require optimal removal of tumor components for expansion.