title: RKTS-33, an epoxycyclohexenone derivative that specifically inhibits Fas ligand-dependent apoptosis in CTL-mediated cytotoxicity.
abstract: Cytotoxic T lymphocytes (CTLs) eliminate virus-infected cells and tumor cells by two distinct killing pathways, mediated by lytic granules containing perforin and by Fas ligand (FasL). ECH [(2R,3R,4S)-2,3-epoxy-4-hydroxy-5-hydroxymethyl-6-(1E)-propenyl-cyclohex-5-en-1-one] has been shown to inhibit FasL-dependent apoptosis or the killing pathway in short-term culture. However, since ECH exhibited cell toxicity in long-term culture, we attempted the synthesis of less toxic epoxycyclohexenone derivatives. In the present study, we found that RKTS-33 [(2R,3R,4S)-2,3-epoxy-4-hydroxy-5-hydroxymethyl-cyclohex-5-en-1-one] has cell toxicity lower than ECH in long-term culture, and further investigated the inhibitory effect of RKTS-33 on CTL-mediated killing pathways. RKTS-33 did not affect cell-surface expression of FasL upon CD3 stimulation, but profoundly inhibited the FasL-dependent killing pathway mediated by CD4+ and CD8+ CTLs, indicating that RKTS-33 specifically blocks target cell apoptosis but not CTL function. By contrast, RKTS-33 did not affect the perforin-dependent killing pathway in CD8+ CTLs. These results indicate that RKTS-33 is a specific inhibitor of the FasL-dependent killing pathway in CTL-mediated cytotoxicity.
authors.affiliation: Center for Biological Resources and Informatics, Tokyo Institute of Technology, Yokohama, Japan.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Mitsui
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Miyake
authors.forename: Hideaki
authors.initials: H
authors.lastname: Kakeya
authors.forename: Yujiro
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Osada
authors.forename: Takao
authors.initials: T
authors.lastname: Kataoka
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002460:Cell Line; D003512:Cyclohexanones / Q000494:pharmacology* / Q000633:toxicity; D003594:Cytoplasmic Granules; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D053938:DNA Fragmentation / Q000187:drug effects; D004852:Epoxy Compounds; D005089:Exocytosis / Q000187:drug effects; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins / Q000032:analysis / Q000187:drug effects / Q000502:physiology; D051379:Mice; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D048069:Tumor Necrosis Factors / Q000032:analysis / Q000502:physiology
chemical_list: D003512:Cyclohexanones; D004852:Epoxy Compounds; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D048069:Tumor Necrosis Factors; D054353:Perforin