FIGURE 1: Immunosuppressive functions of MDSCs in the tumor microenvironment. The cartoon shows cellular interactions of MDSCs with tumors and immune cells and key cellular factors produced by MDSCs and tumors that promote an immunosuppressive environment both systemically and within the tumor. MDSCs can suppress anti-tumor functions of immune cells, but promote other immunosuppressive cells such as Treg and TAM as well as tumor growth and metastasis. The key cellular factors include cytokines, chemokines, surface receptors, enzymes, and metabolites.