The involvement of STAT signaling in the immunosuppressive activity of MDSC in cancer has been further evidenced in studies on human head and neck squamous cell carcinoma and breast cancer, suggesting a pivotal role of STAT3 and STAT1 pathways, respectively, for MDSC suppressive activity within cancer microenvironment (Hix et al., 2013; Vasquez-Dunddel et al., 2013). This evidence concerns the gene STAT3 and cancer.