The results showed that among the thirty-three tumors associated with gene expression, IDO1 mRNA was highly expressed in twelve tumors in CESC, BRCA, ESCA, HNSC, GBM, KICH, KIRC, KIRP, PCPG, LIHC, STAD, and UCEC by TCGA database; especially overexpressed in CESC, KIRC, HNSC, and UCEC. Here, IDO1 is linked to glioblastoma.