title: Ceramide-tamoxifen regimen targets bioenergetic elements in acute myelogenous leukemia.
abstract: The objective of our study was to determine the mechanism of action of the short-chain ceramide analog, C6-ceramide, and the breast cancer drug, tamoxifen, which we show coactively depress viability and induce apoptosis in human acute myelogenous leukemia cells. Exposure to the C6-ceramide-tamoxifen combination elicited decreases in mitochondrial membrane potential and complex I respiration, increases in reactive oxygen species (ROS), and release of mitochondrial proapoptotic proteins. Decreases in ATP levels, reduced glycolytic capacity, and reduced expression of inhibitors of apoptosis proteins also resulted. Cytotoxicity of the drug combination was mitigated by exposure to antioxidant. Cells metabolized C6-ceramide by glycosylation and hydrolysis, the latter leading to increases in long-chain ceramides. Tamoxifen potently blocked glycosylation of C6-ceramide and long-chain ceramides. N-desmethyltamoxifen, a poor antiestrogen and the major tamoxifen metabolite in humans, was also effective with C6-ceramide, indicating that traditional antiestrogen pathways are not involved in cellular responses. We conclude that cell death is driven by mitochondrial targeting and ROS generation and that tamoxifen enhances the ceramide effect by blocking its metabolism. As depletion of ATP and targeting the "Warburg effect" represent dynamic metabolic insult, this ceramide-containing combination may be of utility in the treatment of leukemia and other cancers.
authors.affiliation: Department of Biochemistry and Molecular Biology East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, NC.
authors.forename: Samy A F
authors.initials: SA
authors.lastname: Morad
authors.affiliation: Department of Biochemistry and Molecular Biology East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, NC.
authors.forename: Terence E
authors.initials: TE
authors.lastname: Ryan
authors.affiliation: Department of Biochemistry and Molecular Biology East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, NC.
authors.forename: P Darrell
authors.initials: PD
authors.lastname: Neufer
authors.affiliation: Department of Biochemistry and Molecular Biology East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, NC.
authors.forename: Tonya N
authors.initials: TN
authors.lastname: Zeczycki
authors.affiliation: Department of Biochemistry and Molecular Biology East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, NC.
authors.forename: Traci S
authors.initials: TS
authors.lastname: Davis
authors.affiliation: Department of Biochemistry and Molecular Biology East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, NC.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: MacDougall
authors.affiliation: Cancer Center, Division of Hematology Oncology, Department of Medicine Department of Pharmacology, University of Virginia, Charlottesville, VA.
authors.forename: Todd E
authors.initials: TE
authors.lastname: Fox
authors.affiliation: Department of Pharmacology, Faculty of Veterinary Medicine, South Valley University, Qena, Egypt.
authors.forename: Su-Fern
authors.initials: SF
authors.lastname: Tan
authors.affiliation: Cancer Center, Division of Hematology Oncology, Department of Medicine Oncology, Department of Medicine.
authors.forename: David J
authors.initials: DJ
authors.lastname: Feith
authors.affiliation: Cancer Center, Division of Hematology Oncology, Department of Medicine Department of Pharmacology, Faculty of Veterinary Medicine, South Valley University, Qena, Egypt.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Loughran
authors.affiliation: Cancer Center, Division of Hematology Oncology, Department of Medicine.
authors.forename: Mark
authors.initials: M
authors.lastname: Kester
authors.affiliation: Penn State Hershey Cancer Institute, The Pennsylvania State University, Hershey, PA.
authors.forename: David F
authors.initials: DF
authors.lastname: Claxton
authors.affiliation: Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH.
authors.forename: Brian M
authors.initials: BM
authors.lastname: Barth
authors.affiliation: East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, NC.
authors.forename: Tye G
authors.initials: TG
authors.lastname: Deering
authors.affiliation: Department of Biochemistry and Molecular Biology East Carolina Diabetes and Obesity Institute, Brody School of Medicine, East Carolina University, Greenville, NC cabotm@ecu.edu.
authors.forename: Myles C
authors.initials: MC
authors.lastname: Cabot
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D002518:Ceramides / Q000008:administration & dosage*; D004357:Drug Synergism; D042967:Electron Transport Complex I / Q000187:drug effects; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013629:Tamoxifen / Q000008:administration & dosage*
chemical_list: D002518:Ceramides; D017382:Reactive Oxygen Species; C101954:N-caproylsphingosine; D013629:Tamoxifen; D000255:Adenosine Triphosphate; D042967:Electron Transport Complex I
keywords: ceramides; leukemia; mitochondria; sphingolipids