Correlation between myeloid-derived suppressor cells and S100A8/A9 in tumor and autoimmune diseases

•MDSCs synthesized and secreted S100A8/A9 in tumor environment•Signaling pathways involved in MDSCs-S100A8/A9 interaction•Signaling pathways involved in S100A8/A9-tumor cells interaction•The role of MDSCs and S100A8/A9 in autoimmune diseases

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells that constitute an important component of immune regulatory system. Two calcium-binding proteins S100A8 and S100A9 act as important mediators in acute and chronic inflammation. In recent years, many researchers have found that MDSCs and S100A8/A9 operated with one another through a positive feedback loop to promote tumor development and metastasis. However, the correlation between MDSCs and S100A8/A9 in autoimmune diseases (AIDs) remains unknown. In this review, we discussed the co-operation of MDSCs and S100A8/A9 in tumor environment, and also, the role of these two components in AIDs.