Under the effects of various factors secreted by tumor cells, MDSCs secreted a variety of proproliferative, proinflammatory, and immunosuppressive molecules via activating their own S1PR1‐STAT3, TGF‐β, and other signaling pathways, to make local blood vessels hyperpermeable, to build pre‐metastatic microenvironments, to promote the recruitment, seeding, and expansion of tumor cells, and to provide conditions for the formation of metastases.34, 35. Here, STAT3 is linked to neoplasm.