In different types of tumors, cancer cells produce factors involved in the myelopoiesis (VEGF, GM-CSF, IL-1β, IL-6, HIF-1α, TGF-β, COX-2), as well as in the recruitment (CCL2, CCL3) and activation (TNF-α, IL-10, IL-1β, IL-6, INF-γ, COX-2, HIF-1α) of MDSCs [8,11]. Here, PTGS2 is linked to cancer.