As shown in Figure 3E, compared to those of splenic MDSCs from tumor-bearing mice, ATRA treatment alone slightly increased the expression levels of some inflammatory molecules in MDSCs, such as IL-12, IL-7, and IL-15, but the level of IL-6, which is considered a chronic inflammatory cytokine and plays a major role in MDSC-induced immunosuppression (18), was also increased. This evidence concerns the gene IL15 and neoplasm.