We therefore investigated the relationship between IDO1 and angiogenesis-related genes VEGFA, MMP2, MMP9, CD34, as well as the association between the mRNA expression levels of these genes and the pathological grade or prognosis of glioma patients, using glioma patient data from the Chinese Glioma Genome Atlas (CGGA [36]). Here, CD34 is linked to central nervous system cancer.