title: STAT1 signaling regulates tumor-associated macrophage-mediated T cell deletion.
abstract: It is well established that tumor progression is associated with the accumulation of myeloid suppressive cells, which in mice include Gr-1+ immature myeloid cells and F4/80+ macrophages. The paradox is that with the exception of terminal stages of the disease or chemotherapy treatment, tumor-bearing mice or cancer patients do not display a profound systemic immune suppression. We therefore raised the question as to whether myeloid cell-mediated T cell suppression is controlled at a local level at the site of the tumor. We have demonstrated that after adoptive transfer to tumor-bearing recipients, Gr-1+ (immature myeloid cells) freshly isolated from spleens of tumor-bearing mice become F4/80+ tumor-associated macrophages (TAM). These TAM, but not F4/80+ macrophages or Gr-1+ cells freshly isolated from spleens of tumor-bearing or naive mice were able to inhibit T cell-mediated immune response in vitro via induction of T cell apoptosis. Arginase and NO were both responsible for the apoptotic mechanism, and were seen only in TAM, but not in freshly isolated Gr1+ cells. Using the analysis of STAT activity in combination with STAT knockout mice, we have determined that STAT1, but not STAT3 or STAT6, was responsible for TAM-suppressive activity.
authors.affiliation: H. Lee Moffitt Cancer Center, University of South Florida, Tampa, FL 33612, USA. kusmarsa@moffitt.usf.edu
authors.forename: Sergei
authors.initials: S
authors.lastname: Kusmartsev
authors.forename: Dmitry I
authors.initials: DI
authors.lastname: Gabrilovich
mesh_terms: D000818:Animals; D017209:Apoptosis; D001119:Arginase / Q000378:metabolism; D002454:Cell Differentiation; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D005260:Female; D007108:Immune Tolerance; D008212:Lymphocyte Depletion; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009374:Neoplasms, Experimental / Q000276:immunology* / Q000473:pathology; D009569:Nitric Oxide / Q000096:biosynthesis; D050794:STAT1 Transcription Factor; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology* / Q000473:pathology; D015534:Trans-Activators / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D050794:STAT1 Transcription Factor; C494080:Stat1 protein, mouse; D015534:Trans-Activators; D009569:Nitric Oxide; D001119:Arginase