title: Role of STAT3 in CD4+CD25+FOXP3+ regulatory lymphocyte generation: implications in graft-versus-host disease and antitumor immunity.
abstract: Immunological tolerance is maintained by specialized subsets of T cells including CD4(+)CD25(+)FOXP3(+) regulatory cells (Treg). Previous studies established that Treg thymic differentiation or peripheral conversion depend on CD28 and Lck signaling. Moreover, foxp3 gene transfer in murine CD4(+)CD25(-) T lymphocytes results in the acquisition of suppressive functions. However, molecular pathways leading to FOXP3 expression remain to be described. In this study, we investigated the molecular events driving FOXP3 expression. We demonstrated that CD28 activation in CD4(+)CD25(-) T lymphocytes leads to STAT3 Tyr(705) phosphorylation in an Lck-dependent manner. STAT3 neutralization during naive peripheral CD4(+)CD25(-) T cell conversion into Treg through costimulation with TCR/CD28 and TGF-beta1, decreased FOXP3 expression, prevented the acquisition of suppressive functions and restored the ability of the converted lymphocytes to produce IL-2 and IFN-gamma. Furthermore, we observed that STAT3 ablation using small interfering RNA strategies inhibited FOXP3 expression and suppressive functions among naturally differentiated CD4(+)CD25(+) T lymphocytes, suggesting a direct role of STAT3 in Treg phenotype and function maintenance. CD4(+)CD25(+) T lymphocytes transduced with specific STAT3 small interfering RNA were devoid of suppressive functions and failed to control the occurrence of acute graft-vs-host disease. Finally, STAT3 inhibition in CD4(+) lymphocytes enhanced the anti-tumor immunity conferred by a lymphocyte adoptive transfer. In summary, our findings determine that STAT3 is critical in the molecular pathway required for FOXP3 expression. STAT3 modulation should be taken into account when assessing how regulatory T cells contribute to inflammatory diseases and tumor immunosurveillance.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale U645, EFS Bourgogne Franche Comté, University of Franche-Comté, Besançon, France.
authors.forename: Jean-René
authors.initials: JR
authors.lastname: Pallandre
authors.forename: Emilie
authors.initials: E
authors.lastname: Brillard
authors.forename: Gilles
authors.initials: G
authors.lastname: Créhange
authors.forename: Amandine
authors.initials: A
authors.lastname: Radlovic
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Remy-Martin
authors.forename: Philippe
authors.initials: P
authors.lastname: Saas
authors.forename: Pierre-Simon
authors.initials: PS
authors.lastname: Rohrlich
authors.forename: Xavier
authors.initials: X
authors.lastname: Pivot
authors.forename: Xiang
authors.initials: X
authors.lastname: Ling
authors.forename: Pierre
authors.initials: P
authors.lastname: Tiberghien
authors.forename: Christophe
authors.initials: C
authors.lastname: Borg
mesh_terms: D000818:Animals; D018106:CD28 Antigens / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D051858:Forkhead Transcription Factors / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000276:immunology; D006086:Graft vs Host Disease / Q000276:immunology*; D016219:Immunotherapy, Adoptive / Q000379:methods*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000276:immunology*; D010641:Phenotype; D010766:Phosphorylation; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology* / Q000637:transplantation
chemical_list: D018106:CD28 Antigens; D017252:CD3 Complex; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse