title: Tpl2 and ERK transduce antiproliferative T cell receptor signals and inhibit transformation of chronically stimulated T cells.
abstract: The protein kinase encoded by the Tpl2 protooncogene plays an obligatory role in the transduction of Toll-like receptor and death receptor signals in macrophages, B cells, mouse embryo fibroblasts, and epithelial cells in culture and promotes inflammatory responses in animals. To address its role in T cell activation, we crossed the T cell receptor (TCR) transgene 2C, which recognizes class I MHC presented peptides, into the Tpl2(-/-) genetic background. Surprisingly, the TCR2C(tg/tg)/Tpl2(-/-) mice developed T cell lymphomas with a latency of 4-6 months. The tumor cells were consistently TCR2C(+)CD8(+)CD4(-), suggesting that they were derived either from chronically stimulated mature T cells or from immature single positive (ISP) cells. Further studies showed that the population of CD8(+) ISP cells was not expanded in the thymus of TCR2C(tg/tg)/Tpl2(-/-) mice, making the latter hypothesis unlikely. Mature peripheral T cells of Tpl2(-/-) mice were defective in ERK activation and exhibited enhanced proliferation after TCR stimulation. The same cells were defective in the induction of CTLA4, a negative regulator of the T cell response, which is induced by TCR signals via ERK. These findings suggest that Tpl2 functions normally in a feedback loop that switches off the T cell response to TCR stimulation. As a result, Tpl2, a potent oncogene, functions as a tumor suppressor gene in chronically stimulated T cells.
authors.affiliation: Department of Clinical Chemistry, and Graduate Program on the Molecular Basis of Human Disease, School of Medicine, University of Crete, Heraklion, 710 03 Crete, Greece. tsatsani@med.uoc.gr
authors.forename: Christos
authors.initials: C
authors.lastname: Tsatsanis
authors.forename: Katerina
authors.initials: K
authors.lastname: Vaporidi
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Zacharioudaki
authors.forename: Ariadne
authors.initials: A
authors.lastname: Androulidaki
authors.forename: Yuri
authors.initials: Y
authors.lastname: Sykulev
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Margioris
authors.forename: Philip N
authors.initials: PN
authors.lastname: Tsichlis
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D000943:Antigens, Differentiation / Q000378:metabolism; D015153:Blotting, Western; D060908:CTLA-4 Antigen; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000235:genetics; D048049:Extracellular Signal-Regulated MAP Kinases / Q000276:immunology / Q000378:metabolism*; D005434:Flow Cytometry; D007150:Immunohistochemistry; D020930:MAP Kinase Kinase Kinases / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D011518:Proto-Oncogene Proteins / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D019076:Transgenes / Q000235:genetics
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; C556707:Ctla4 protein, mouse; D011518:Proto-Oncogene Proteins; D048049:Extracellular Signal-Regulated MAP Kinases; D020930:MAP Kinase Kinase Kinases; C489843:Map3k8 protein, mouse