Additionally, serum S100A9 levels and MDSC numbers were positively correlated to each other in CRC patients (Figure 3A), and there was also a positive correlation of serum S100A9 levels with Arg-1 and iNOS levels, two immunosuppressive molecules mainly expressed and secreted by MDSCs, in CRC (Figures 3B,C). Here, S100A9 is linked to colorectal carcinoma.