title: Immune escape of tumors in vivo by expression of cellular FLICE-inhibitory protein.
abstract: The antiapoptotic protein cellular FLICE (Fas-associated death domain-like IL-1beta-converting enzyme) inhibitory protein (cFLIP) protects cells from CD95(APO-1/Fas)-induced apoptosis in vitro and was found to be overexpressed in human melanomas. However, cytotoxic T cell-induced apoptosis, which is critically involved in tumor control in vivo, is not inhibited by cFLIP in vitro, as only CD95- and not perforin-dependent lysis is affected. This calls into question whether cFLIP is sufficient to allow escape from T cell-dependent immunity. Using two murine tumors, we directly demonstrate that cFLIP does result in escape from T cell immunity in vivo. Moreover, tumor cells are selected in vivo for elevated cFLIP expression. Therefore, our data indicate that CD95-dependent apoptosis constitutes a more prominent mechanism for tumor clearance than has so far been anticipated and that blockade of this pathway can result in tumor escape even when the perforin pathway is operational.
authors.affiliation: Department of Immunohematology and Bloodbank, Leiden University Medical Center, 2333AA Leiden, The Netherlands. medema@mail.medfac.leidenuniv.nl
authors.forename: J P
authors.initials: JP
authors.lastname: Medema
authors.forename: J
authors.initials: J
authors.lastname: de Jong
authors.forename: T
authors.initials: T
authors.lastname: van Hall
authors.forename: C J
authors.initials: CJ
authors.lastname: Melief
authors.forename: R
authors.initials: R
authors.lastname: Offringa
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000235:genetics* / Q000502:physiology*; D003001:Cloning, Molecular; D003602:Cytotoxicity, Immunologic; D005260:Female; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008562:Membrane Glycoproteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009374:Neoplasms, Experimental / Q000276:immunology* / Q000473:pathology; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D011994:Recombinant Proteins / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014162:Transfection; D019014:fas Receptor / Q000502:physiology*
chemical_list: D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; C506387:Cflar protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D011994:Recombinant Proteins; D019014:fas Receptor; D054353:Perforin