History of myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) remain steeped in mystery and controversy — how do we identify them? How are they recruited to the tumour microenvironment? How do they suppress antitumour immunity? This Timeline article discusses the discovery of MDSCs and what we know now — and need to know in the future — about the role of MDSCs in cancer biology. Tumour-induced granulocytic hyperplasia is associated with tumour vasculogenesis and escape from immunity via T cell suppression. Initially, these myeloid cells were identified as granulocytes or monocytes; however, recent studies have revealed that this hyperplasia is associated with populations of multipotent progenitor cells that have been identified as myeloid-derived suppressor cells (MDSCs). The study of MDSCs has provided a wealth of information regarding tumour pathobiology, has extended our understanding of neoplastic progression and has modified our approaches to immune adjuvant therapy. In this Timeline article, we discuss the history of MDSCs, their influence on tumour progression and metastasis, and the crosstalk between tumour cells, MDSCs and the host macroenvironment.