IDO1 and gastric cancer: The expression of certain immunosuppressive markers (FOXP3, Tim3, ICOS, CD163,) including PMN-MDSC markers (ARG1, CD66b, VISTA and IDO1) were significantly (p < 0.01) higher in the FFPE gastric cancer patient tissues which exhibited a higher expression of HER2 and PD-L1 (Figure 3c), when compared to HER2 and PD-L1 negative gastric cancer patient tissues.