title: Ceramide-induced killing of normal and malignant human lymphocytes is by a non-apoptotic mechanism.
abstract: Synthetic ceramides induce apoptotic death of Jurkat and HL60 leukaemia cell lines. By contrast we show here that ceramide induces non-apoptotic killing of malignant cells from patients with B-chronic lymphocytic leukaemia (B-CLL) and of normal B lymphocytes. The protein phosphatase inhibitor okadaic acid readily induces apoptosis of B-CLL cells, indicating that this death pathway is fully functional in these cells. The ability of ceramide to activate the apoptotic protease caspase 3 in HL60 cells but not in B-CLL cells, as well as the lack of correlation of ceramide-mediated killing of different B-CLL isolates with expression of the apoptosis-regulating proteins bcl-2 and bax reinforce the conclusion that ceramide killing of B-CLL cells is by a non-apoptotic mechanism. Fludarabine treatment or gamma-irradiation of B-CLL cells resulted in ceramide elevation and in killing by both apoptotic and non-apoptotic mechanisms, suggesting that a ceramide-triggered non-apoptotic mechanism may play a role in the killing of these cells. Therefore, the results here show that ceramide can induce either apoptotic or non-apoptotic death, depending on the cellular context. The inability of synthetic dihydroceramide to kill B-CLL cells or normal B lymphocytes suggests that non-apoptotic killing by ceramide is via interaction with a specific, but unidentified, cellular target.
authors.affiliation: Department of Hematology, Royal Free and University College School of Medicine, London, UK.
authors.forename: K
authors.initials: K
authors.lastname: Mengubas
authors.forename: F A
authors.initials: FA
authors.lastname: Riordan
authors.forename: C A
authors.initials: CA
authors.lastname: Bravery
authors.forename: J
authors.initials: J
authors.lastname: Lewin
authors.forename: D L
authors.initials: DL
authors.lastname: Owens
authors.forename: A B
authors.initials: AB
authors.lastname: Mehta
authors.forename: A V
authors.initials: AV
authors.lastname: Hoffbrand
authors.forename: R G
authors.initials: RG
authors.lastname: Wickremasinghe
mesh_terms: D000581:Amidohydrolases / Q000037:antagonists & inhibitors; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D055572:Ceramidases; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005720:Gamma Rays; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy; D008214:Lymphocytes / Q000187:drug effects* / Q000473:pathology* / Q000528:radiation effects; D009226:Myristates / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D014176:Protein Biosynthesis; D011506:Proteins / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014740:Vidarabine / Q000031:analogs & derivatives / Q000494:pharmacology; D051028:bcl-2-Associated X Protein
chemical_list: D000970:Antineoplastic Agents; C494826:BAX protein, human; D004791:Enzyme Inhibitors; D009226:Myristates; C064769:N-acetylsphingosine; D011412:Propanolamines; D011506:Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; C099657:2-(N-myristoylamino)-1-phenyl-1-propanol; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D000581:Amidohydrolases; D055572:Ceramidases; D014740:Vidarabine; D013110:Sphingosine; C024352:fludarabine