IDO1 and breast cancer: In accordance, co-expression data revealed that IDO1 strongly correlated to PDCD1 (PD-1), CD274 (PD-L1), PDCD1LG2 (PD-L2), LAG3 and CTLA4 immune checkpoints and IFNG in BC, with a positive correlation coefficient of 0.77, 0.66, 0.71, 0.76, 0.75 and 0.77, predicting that these genes could participate into the immunosuppressive biological process involving T cell dynamics (Fig. 3B).