title: Flavopiridol causes early mitochondrial damage in chronic lymphocytic leukemia cells with impaired oxygen consumption and mobilization of intracellular calcium.
abstract: Effective administration of flavopiridol in advanced-stage chronic lymphocytic leukemia (CLL) is often associated with early biochemical evidence of tumor cell lysis. Previous work using other cell types showed that flavopiridol impacts mitochondria, and in CLL cells flavopiridol down-regulates the mitochondrial protein Mcl-1. We therefore investigated mitochondrial structure and function in flavopiridol-treated CLL patient cells and in the lymphoblastic cell line 697 using concentrations and times at which tumor lysis is observed in treated patients. Mitochondrial membrane depolarization was detected in flavopiridol-treated CLL cells by 6 hours, well before the onset of cell death. Flavopiridol-induced mitochondrial depolarization was not blocked by caspase inhibitors or by the calcium chelator EGTA, but was reduced by Bcl-2 overexpression. Intracellular calcium mobilization was noted at early time points using fluorescence microscopy. Furthermore, electron paramagnetic resonance oximetry showed a gradual but significant reduction in cellular oxygen consumption rate by 6 hours, corresponding with ultrastructural mitochondrial damage detected by electron microscopy. These observations suggest that in CLL and 697 cells, flavopiridol mediates its cytotoxic effects via induction of the mitochondrial permeability transition and changes in intracellular calcium.
authors.affiliation: Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Syed-Rehan A
authors.initials: SR
authors.lastname: Hussain
authors.forename: David M
authors.initials: DM
authors.lastname: Lucas
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Johnson
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Lin
authors.forename: Alan P
authors.initials: AP
authors.lastname: Bakaletz
authors.forename: Vinh X
authors.initials: VX
authors.lastname: Dang
authors.forename: Serge
authors.initials: S
authors.lastname: Viatchenko-Karpinski
authors.forename: Amy S
authors.initials: AS
authors.lastname: Ruppert
authors.forename: John C
authors.initials: JC
authors.lastname: Byrd
authors.forename: Periannan
authors.initials: P
authors.lastname: Kuppusamy
authors.forename: Elliott D
authors.initials: ED
authors.lastname: Crouser
authors.forename: Michael R
authors.initials: MR
authors.lastname: Grever
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D005419:Flavonoids / Q000494:pharmacology*; D005434:Flow Cytometry; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology*; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D010880:Piperidines / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D061945:Caspase Inhibitors; D005419:Flavonoids; D010880:Piperidines; D019253:Proto-Oncogene Proteins c-bcl-2; C077990:alvocidib; D020169:Caspases; D010100:Oxygen; D002118:Calcium