CD8+ cells infiltrating cancer-cell islets featured higher expression of proteins related to effector function (GZMB, CD127), T-cell co-stimulation and co-inhibition (PD-1, LAG3, 4-1BB, GITR, STING, B7-H3), and other non-T-cell co-inhibitory proteins (PD-L1, PD-L2), IDO1, and Ki-67. This evidence concerns the gene IDO1 and cancer.