title: Fas-Fas ligand-based interactions between tumor cells and tumor-specific cytotoxic T lymphocytes: a lethal two-way street.
abstract: In the current study, we investigated the repercussions of the interaction between tumor cells (LSA) and the tumor-specific cytotoxic T lymphocyte (CTL) (PE-9) when both expressed Fas and Fas ligand (FasL). The CTL clone, PE-9, expressed high levels of Fas and FasL upon activation through the T-cell receptor (TCR). Furthermore, the activated PE-9 cells used both perforin- and FasL-based pathways to kill Fas-positive (Fas+) LSA tumor cells. Interestingly, LSA tumor cells also constitutively expressed FasL but not perforin, and killed Fas+ PE-9 CTLs and Fas+ but not Fas-negative (Fas-) activated T cells and thymocytes, as detected using the JAM test. PE-9 CTLs, cultured for 24 hours in the presence of cell lysates of FasL-bearing LSA cells but not FasL-deficient P815 cells, exhibited significant apoptosis as detected using the TUNEL method. Moreover, another FasL+ T-cell lymphoma line, EL-4, induced apoptosis in Fas+ but not in Fas- T cells in a similar fashion. The current study demonstrates for the first time that not only can the tumor-specific CTL mediate Fas-based killing of tumor cells, but FasL+ tumor cells can kill the Fas+ tumor-specific CTL. Thus, the survival of the tumor or the host may depend on which cell can accomplish this task more efficiently. The current study also suggests that FasL-based killing of CTLs by specific tumor cells may constitute a major limiting factor in successful immunotherapy.
authors.affiliation: Department of Biology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg 24061, USA.
authors.forename: A
authors.initials: A
authors.lastname: Zeytun
authors.forename: M
authors.initials: M
authors.lastname: Hassuneh
authors.forename: M
authors.initials: M
authors.lastname: Nagarkatti
authors.forename: P S
authors.initials: PS
authors.lastname: Nagarkatti
mesh_terms: D000818:Animals; D003602:Cytotoxicity, Immunologic; D053222:Fas Ligand Protein; D005260:Female; D005434:Flow Cytometry; D008562:Membrane Glycoproteins / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009374:Neoplasms, Experimental / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000276:immunology*
chemical_list: D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D019014:fas Receptor