On the origin of myeloid-derived suppressor cells

// Camilla Rydberg Millrud 1 , Caroline Bergenfelz 2 and Karin Leandersson 1 1 Department of Translational Medicine, Cancer Immunology, Lund University, Skåne University Hospital, Malmö, Sweden 2 Department of Translational Medicine, Division of Experimental Infection Medicine, Lund University, Malmö, Sweden Correspondence to: Camilla Rydberg Millrud, email: // Keywords : MDSC origin, myelopoiesis, emergency myelopoiesis, reprogramming, extramedullary Received : July 22, 2016 Accepted : September 20, 2016 Published : September 27, 2016 Abstract Myeloid-derived suppressor cells (MDSCs) have a strong immunosuppressive character that allows them to regulate immune responses and hinder overt inflammatory responses. In cancer, this leads to tumor immune evasion and disease progression. MDSCs come in at least two forms: monocytic (Mo-MDSCs) and granulocytic (G-MDSCs). The classical definition of MDSCs as immature myeloid cells blocked from differentiating has been challenged by recent studies suggesting that Mo-MDSCs and G-MDSCs may represent monocytes and granulocytes that have acquired immunosuppressive properties. The molecular mechanism behind their generation and their true origins are now widely debated. In this review we discuss the different proposed mechanisms of the generation of both types of MDSCs, with a special focus on human MDSCs in cancer.