In the immune microenvironment of PCa, MDSCs and Tregs form a synergistic immunosuppressive network through a triple interaction of “chemoattractants-cytokines-metabolites”: On one hand, TGF-β, secreted by tumor cells and Tregs binds to TGF-βRII on the surface of MDSCs, activating Smad2/3 phosphorylation and upregulating the expression of Arg-1 and CCL22, thereby enhancing the metabolic suppression mediated by MDSCs (36). Here, CCL22 is linked to neoplasm.