title: gamma-Tocopheryl quinone induces apoptosis in cancer cells via caspase-9 activation and cytochrome c release.
abstract: Recently, it was suggested the potential role of gamma-tocopheryl quinone (gamma-TQ), an oxidative metabolite of gamma-tocopherol, as a powerful chemotherapeutic agent, since it was shown that this molecule exerts powerful cytotoxic effects, induces apoptosis and escapes drug resistance in human acute lymphoblastic leukemia and promyelocytic leukemia cells. We have studied the apoptogenic potential of gamma-TQ in cultured human leukemia HL-60 and colon adenocarcinoma WiDr cells, and in murine thymoma cells growing in vivo in ascites form. The cells were treated with gamma-TQ and apoptosis was evaluated morphologically by acridine-orange staining and cytofluorimetrically by Annexin V binding assay. gamma-TQ-induced apoptosis in a dose- and time-dependent manner in all the cell types tested, although HL-60 and thymoma cells were much more sensitive than WiDr cells. In HL-60 cells apoptosis was mediated by the activation of the caspase-3 cascade. In particular, we observed a time- and dose-dependent increase in the activities of the upstream caspase-9 and caspase-8 and of the downstream caspase-3. The activation of caspase-9 preceded that of caspase-8 and its specific inhibition completely prevented apoptosis. These findings and data showing the precocious release of cytochrome c from mitochondria, a decrease in Bcl-2, and a change in mitochondrial transmembrane potential (Delta psi(m)), all suggest that the intrinsic mitochondrial pathway is primarily involved in the development of gamma-TQ-induced apoptosis. The late activation of caspase-8 and data showing the partial cleavage of pro-apoptotic protein BID suggest that the initial activation of caspase-9 may be potentiated by a feedback amplification loop involving the caspase-8/BID pathway.
authors.affiliation: Institutes of General Pathology and Pathology, Catholic University, L.go F.Vito, 1-00168 Rome, Italy. g.calviello@rm.unicatt.it
authors.forename: Gabriella
authors.initials: G
authors.lastname: Calviello
authors.forename: Fiorella
authors.initials: F
authors.lastname: Di Nicuolo
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Piccioni
authors.forename: M Elena
authors.initials: ME
authors.lastname: Marcocci
authors.forename: Simona
authors.initials: S
authors.lastname: Serini
authors.forename: Nicola
authors.initials: N
authors.lastname: Maggiano
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Jones
authors.forename: David G
authors.initials: DG
authors.lastname: Cornwell
authors.forename: Paola
authors.initials: P
authors.lastname: Palozza
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D008928:Mitochondria / Q000201:enzymology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000494:pharmacology*
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; D003574:Cytochrome c Group; D019253:Proto-Oncogene Proteins c-bcl-2; D014810:Vitamin E; C002421:tocopherylquinone; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases