title: The Ca(2+) channel blocker flunarizine induces caspase-10-dependent apoptosis in Jurkat T-leukemia cells.
abstract: Flunarizine is a Ca(2+) channel blocker that can be either cytoprotective or cytotoxic, depending on the cell type that is being examined. We show here that flunarizine was cytotoxic for Jurkat T-leukemia cells, as well as for other hematological maligancies, but not for breast or colon carcinoma cells. Treatment of Jurkat cells with flunarizine resulted in caspase-3 activation, poly (ADP-ribose) polymerase cleavage, and laddering of DNA fragments, all of which are hallmarks of apoptosis. Flunarizine-induced DNA fragmentation was inhibited by the caspase-3 inhibitor z-DEVD-fmk, the caspase-8/caspase-10 inhibitor z-IETD-fmk, and the caspase-10 inhibitor z-AEVD-fmk, but was not reduced in caspase-8-deficient Jurkat cells, indicating the involvement of caspase-10 upstream of caspase-3 activation. Interestingly, FADD recruitment to a death receptor was not involved since flunarizine caused DNA fragmentation in FADD-deficient Jurkat cells. Flunarizine treatment of Jurkat cells also resulted in reactive oxygen species production, dissipation of mitochondrial transmembrane potential, release of cytochrome c from mitochondria, and caspase-9 activation, although none of these events were necessary for apoptosis induction. Collectively, these findings indicate that flunarizine triggers apoptosis in Jurkat cells via FADD-independent activation of caspase-10. Flunarizine warrants further investigation as a potential anti-cancer agent for the treatment of hematological malignancies.
authors.affiliation: Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia, B3H 1X5, Canada.
authors.forename: David M
authors.initials: DM
authors.lastname: Conrad
authors.forename: Suzanne J
authors.initials: SJ
authors.lastname: Furlong
authors.forename: Carolyn D
authors.initials: CD
authors.lastname: Doucette
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: West
authors.forename: David W
authors.initials: DW
authors.lastname: Hoskin
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D053455:Caspase 10 / Q000378:metabolism*; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D005444:Flunarizine / Q000494:pharmacology*; D006801:Humans; D019169:Jurkat Cells; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D009842:Oligopeptides / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; C470795:benzyloxycarbonyl-alanyl-glutamyl-valyl-aspartic acid fluoromethyl ketone; C403753:benzyloxycarbonyl-isoleucyl-glutamyl-threonyl-aspartic acid fluoromethyl ketone; D053455:Caspase 10; D005444:Flunarizine