title: In vivo rejection of tumor cells dependent on CD8 cells that kill independently of perforin and FasL.
abstract: Perforin/granzyme B- and Fas/FasL-mediated killing pathways are the main effector mechanisms of CTL and NK cells in antitumor immune responses. In this study, we investigated the relative role of these two lytic mechanisms in protection of the host from tumor progression, as well as spontaneous metastasis, using the D122 Lewis lung carcinoma and its gene-modified cells. Utilizing perforin knockout mice (B6-PKO) and Fas and FasL mutant (B6-MRL and B6-Smn) mice, we found that perforin expression in the host plays a crucial function in the prevention of metastasis. However, local tumor rejection of an H-2K(b) and B7-1 transfectant, 39.5-B7 cells, was not dependent either on perforin or Fas/FasL expression in vivo. In addition, CTL lysis of 39.5-B7 cells was independent of perforin and Fas/FasL interactions in 18-hour in vitro assays. We also confirmed that CD8 T-cells were responsible for rejecting 39.5-B7 local tumors, yet cytokines, TNF-alpha and gammaIFN were not involved in tumor rejection in vivo. Furthermore, blocking assays using caspase inhibitors (zVAD-fmk, zLETD-fmk and zLEHD-fmk) showed that, whereas caspase activation was partially required to induce 39.5-B7 lysis mediated by the perforin-dependent pathway, 39.5-B7 lysis by CTLs through the perforin-independent mechanism required caspase activation. Thus, these results suggested that perforin, Fas/FasL, gammaIFN and TNF-alpha independent lytic mechanisms, mediated by CD8 T cells, have a crucial role in rejection of 39.5-B7 cells in vivo. Caspase activation is a pre requisite for apoptosis of targets by CTLs.
authors.affiliation: Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Sung-Hyung
authors.initials: SH
authors.lastname: Lee
authors.forename: Erez
authors.initials: E
authors.lastname: Bar-Haim
authors.forename: Arthur
authors.initials: A
authors.lastname: Machlenkin
authors.forename: Ofir
authors.initials: O
authors.lastname: Goldberger
authors.forename: Ilan
authors.initials: I
authors.lastname: Volovitz
authors.forename: Ezra
authors.initials: E
authors.lastname: Vadai
authors.forename: Esther
authors.initials: E
authors.lastname: Tzehoval
authors.forename: Lea
authors.initials: L
authors.lastname: Eisenbach
mesh_terms: D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D018122:B7-1 Antigen / Q000378:metabolism; D018827:Carcinoma, Lewis Lung / Q000276:immunology*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D053222:Fas Ligand Protein; D006183:H-2 Antigens / Q000378:metabolism; D064532:Histocompatibility Antigen H-2D; D007371:Interferon-gamma / Q000037:antagonists & inhibitors; D007694:Killer Cells, Natural / Q000276:immunology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009368:Neoplasm Transplantation; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D018122:B7-1 Antigen; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D064532:Histocompatibility Antigen H-2D; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505654:Tnfsf10 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D054353:Perforin; D007371:Interferon-gamma; D020169:Caspases