title: Pivotal Advance: Tumor-mediated induction of myeloid-derived suppressor cells and M2-polarized macrophages by altering intracellular PGE₂ catabolism in myeloid cells.
abstract: Recent studies suggest that tumor-infiltrated myeloid cells frequently up-regulate COX-2 expression and have enhanced PGE₂ metabolism. This may affect the maturation and immune function of tumor-infiltrated antigen-presenting cells. In vitro studies demonstrate that tumor-derived factors can skew GM-CSF-driven differentiation of T(h)1-oriented myeloid APCs into M2-oriented Ly6C(+)F4/80(+) MDSCs or Ly6C(-)F4/80(+) arginase-expressing macrophages. These changes enable myeloid cells to produce substantial amounts of IL-10, VEGF, and MIP-2. The tumor-mediated inhibition of APC differentiation was associated with the up-regulated expression of PGE₂-forming enzymes COX-2, mPGES1 in myeloid cells, and the simultaneous repression of PGE(2)-catabolizing enzyme 15-PGDH. The presence of tumor-derived factors also led to a reduced expression of PGT but promoted the up-regulation of MRP4, which works as a PGE₂ efflux receptor. Addition of COX-2 inhibitor to the BM cell cultures could prevent the tumor-induced skewing of myeloid cell differentiation, partially restoring cell phenotype and down-regulating the arginase expression in the myeloid APCs. Our study suggests that tumors impair the intracellular PGE(2) catabolism in myeloid cells through simultaneous stimulation of PGE(2)-forming enzymes and inhibition of PGE₂-degrading systems. This tumor-induced dichotomy drives the development of M2-oriented, arginase-expressing macrophages or the MDSC, which can be seen frequently among tumor-infiltrated myeloid cells.
authors.affiliation: Shands Cancer Center and Department of Urology, University of Florida College of Medicine, Gainesville, FL 32610, USA.
authors.forename: Evgeniy
authors.initials: E
authors.lastname: Eruslanov
authors.forename: Irina
authors.initials: I
authors.lastname: Daurkin
authors.forename: Javier
authors.initials: J
authors.lastname: Ortiz
authors.forename: Johannes
authors.initials: J
authors.lastname: Vieweg
authors.forename: Sergei
authors.initials: S
authors.lastname: Kusmartsev
mesh_terms: D000818:Animals; D001119:Arginase / Q000378:metabolism; D001854:Bone Marrow Cells / Q000502:physiology; D003110:Colonic Neoplasms / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D016207:Cytokines / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D007165:Immunosuppression Therapy; D008264:Macrophages / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D022423:Myeloid Cells / Q000276:immunology* / Q000378:metabolism; D010766:Phosphorylation; D050794:STAT1 Transcription Factor / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D016207:Cytokines; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; C494080:Stat1 protein, mouse; C494087:Stat3 protein, mouse; D001119:Arginase; D015232:Dinoprostone