IDO1 and cancer: In specific, TIS is referred to as an 18‐gene signature (CCL5, GZMK, CD3D, CD3E, CD2, HLA‐DRA, IL2RG, NKG7, CIITA, CXCR6, LAG3, TAGAP, HLA‐E, CXCL13, IDO1, CXCL10, STAT1, and GZMB), which was related to the response to ICIs in various cancers.21, 22