IDO1 and head and neck squamous cell carcinoma: We identified immunostimulators (VTCN1, TGFB1, CDC244, LAG3, PDCD1, TIGIT, IDO1, CD274, ADORA2A, KDR) and immunoinhibitors (TNFSF13, TNFSF4, KLRC1, TNFRSF25, IL2RA, CXCR4, ENTPD1, ULBP1, RAET1E, KLRK1, CD276, TMIGD2, IL6, CXCL12, C10ORF54, NT5E, TNFRSF4, TNFRSF13C, CD40, TMEM173) significantly associated with EPHX4 in HNSCC.