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. Author manuscript; available in PMC: 2009 Dec 31.
Published in final edited form as: Nat Biotechnol. 2008 Dec;26(12):1348–1349. doi: 10.1038/nbt1208-1348

Figure 1.

Figure 1

Multiple pro-inflammatory mediators in the tumor microenvironment increase the accumulation of MDS cells and enhance their immunosuppressive activity. MDS cell accumulation is driven by the proinflammatory factors prostaglandin E2 (PGE2), S100A8/A9 proteins, vascular endothelial growth factor (VEGF), cytokines IL-1β and IL-6, and complement component C5a (ref. 1), all of which are produced in the tumor microenvironment by host stromal cells. COX2 and PGE2 can also be secreted by tumor cells. MDS cells express receptors for all of these molecules except IL-1β. Besides increasing MDS cell abundance and potency, C5a and S100A8/A9 proteins are chemotactic, attracting MDS cells to tumor sites. VEGF and S100A8/A9 proteins are produced by both MDS and other host cells, providing an autocrine regulatory pathway for maintaining MDS cell levels. By activating MDS cells, these pro-inflammatory mediators inhibit anti-tumor immunity and interfere with cell-mediated immunotherapies.