Myeloid-Derived Suppressor Cells in Cancers and Inflammatory Diseases: Angel or Demon?

Myeloid-derived suppressor cell (MDSC) is an important heterogeneous cell population that regulates innate and adaptive immune. The immunosuppressive potentiality is widely known. However, more and more data indicated that the heterogeneous cell population had immunostimulatory activities rather than immunosuppression in some microenvironments. Chronic inflammatory conditions contribute to accumulation of MDSCs. These pathologically activated cells played critical roles in cancer and inflammatory diseases. In this review, we mainly discuss the immunoregulation potentiality of MDSCs in cancer and inflammatory diseases.