title: Daunorubicin- and Ara-C-induced interphasic apoptosis of human type II leukemia cells is caspase-8-independent.
abstract: Drug-induced interphasic apoptosis in human leukemia cells is mediated through intracellular signaling pathways, of which the most proximal (initiating) event remains unclear. Indeed, both early ceramide generation and procaspase-8 cleavage have been individually identified as the initial apoptotic signaling events which precede the mitochondrial control of the apoptotic execution phase in Type II cells. In order to evaluate whether or not procaspase-8 cleavage is requisite for initial ceramide generation and rapid interphasic apoptosis, we investigated the chronological ordering of early ceramide generation and caspase-8 cleavage induced by daunorubicin (DNR) and 1-beta-D-arabinofuranosylcytosine (Ara-C) in U937 cells. We further evaluated the impact of these two drugs on initial ceramide generation and apoptosis in wild-type Jurkat cells and Jurkat clones mutated for caspase-8 and Fas-associated death domain. We show that while both DNR and Ara-C similarly induced early ceramide generation (within 5-20 min) and interphasic apoptosis in all cell models, caspase-8 cleavage was only observed farther downstream (4.5 h) and only in DNR-treated cells. Furthermore, neither DNR or Ara-C induced caspase-8 activation. These results demonstrate that caspase-8 cleavage is not requisite for the drug-induced activation of the ceramide-mediated interphasic apoptotic pathway in human Type II leukemic cells.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale E9910, Institut Claudius Régaud, 20 rue Pont St Pierre, 31052 Toulouse, France.
authors.forename: Anne-Dominique
authors.initials: AD
authors.lastname: Terrisse
authors.forename: Christine
authors.initials: C
authors.lastname: Bezombes
authors.forename: Sandra
authors.initials: S
authors.lastname: Lerouge
authors.forename: Guy
authors.initials: G
authors.lastname: Laurent
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Jaffrézou
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis; D002352:Carrier Proteins / Q000032:analysis / Q000235:genetics; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000032:analysis* / Q000235:genetics; D002518:Ceramides / Q000032:analysis* / Q000096:biosynthesis; D003561:Cytarabine / Q000494:pharmacology*; D004249:DNA Damage; D003630:Daunorubicin / Q000494:pharmacology*; D053200:Fas-Associated Death Domain Protein; D006801:Humans; D007399:Interphase; D019169:Jurkat Cells; D007938:Leukemia; D009154:Mutation; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D002518:Ceramides; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D003561:Cytarabine; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D003630:Daunorubicin