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. 2010 Jan 27;5(1):e8922. doi: 10.1371/journal.pone.0008922

Figure 7. A model of the closed loop among mast cells, MDSCs and Treg cells in tumor microenvironment.

Figure 7

Under the guidance of SCF/c-kit signaling, mast cells migrate to and are activated in tumor microenvironment; the activated mast cells release a panel of factors, leading to CCL2 production and IL-17 upregulation in MDSCs; CCL2 signaling recruits more MDSCs, leading to more IL-17 production; IL-17 strengthens tumor inflammatory microenvironment, leading to the upregulation of IL-9, IL-10, IL-13, CCL17, CCL22, CD39 and CD73; IL-10 and IL-13 induce arginase 1 expression by MDSCs; CCL17 and CCL22 attract the migration of Treg cells; CD39 and CD73 enhance suppressor function of Treg cells; IL-9 produced by Treg cells maintains the survival of mast cells; MDSCs release active MMP9, through which soluble SCF is generated, thus further facilitating the migration and activation of mast cells.