Phenotypic and functional dissection of myeloid-derived suppressor cells

Abstract

Myeloid-derived suppressor cells (MDSCs) are originated and differentiated population from common hematopoietic progenitor cells. Generally, in the late stage of inflammation, MDSCs differentiation and expansion are promoted to suppress the over-activated immune system so that the immune system can maintain the homeostasis. Recently, it has been revealed that MDSCs accumulate in cancer patients and tumor-bearing experimental animals, and these tumor-derived MDSCs suppress anti-tumor immunity by secreting immunosuppressive cytokines including reactive oxygen species and inducible nitric oxide synthase. This fact prompts scientists to shed light on MDSCs as significant targets for anti-cancer immunotherapy. However, due to morphological, phenotypic, and functional heterogeneities of MDSCs, it is not easy to develop therapeutic strategies targeting MDSCs. In this review, we will summarize recent progress on defined subsets of MDSCs and their strategies to suppress T cell-mediated anti-tumor immunity.