From numerical amplification to functional metamorphosis: the MDSC-driven therapeutic resistance in tumor

Myeloid-derived suppressor cells (MDSCs) are a population with immunosuppressive characteristics in the tumor microenvironment, which are linked to poor prognosis and therapeutic resistance across cancers. In this review, a novel concept of MDSCs and a quantity-quality pattern are proposed to illustrate the spatiotemporal dynamics of MDSC fate. By reviewing current researches through this framework, a group of pro-tumor signals is identified to have critical roles in the whole life cycle of MDSC evolution, including immature myeloid cell proliferation, differentiation education, suppressive functioning of MDSCs, and targeting strategy.