TANs have pro-tumor activity by producing ARG1, IL-10, TGF-β, and VEGF, and inhibiting cytotoxic T cells by expressing higher levels of immunosuppressive molecules, such as PD-L1, ARG1, and IDO, and lower of anti-tumor molecules, such as ROS and TNF-α (37, 38). The gene discussed is IDO1; the disease is neoplasm.