IDO1 and head and neck squamous cell carcinoma: Overall survival analysis in TCGA HNSCC database showed that CD276, LDHB, SLC3A2, EGFR, SLC7A5, and HPRT1 were potential unfavorable prognosis markers in HNSCC (Figures 7A–F), while EEA1, IDO1, NCOA2, REST, CCL19, and ALDH2 were potential favorable prognosis markers in HNSCC (Figures 7G–L).