IDO1 and glioblastoma: Importantly, IDO1 expression in tumor cells increased with the increased expression of markers of TAMs (such as HLA-DRA and CD163) and neutrophils (for example, CD11b and CD16), and with multiple lymphocitic markers, including FOXP3, PD-1 and PD-L1, suggesting that T-cells directly regulate IDO1 expression in human GBM.