title: Bovine lactoferricin selectively induces apoptosis in human leukemia and carcinoma cell lines.
abstract: Bovine lactoferricin (LfcinB) is a cationic, amphipathic peptide that is cytotoxic for human and rodent cancer cells. However, the mechanism by which LfcinB causes the death of cancer cells is not well understood. Here, we show that in vitro treatment with LfcinB rapidly induced apoptosis in several different human leukemia and carcinoma cell lines as determined by DNA fragmentation assays and phosphatidylserine headgroup inversion detected by Annexin V binding to the surface of cancer cells. Importantly, LfcinB treatment did not adversely affect the viability of untransformed human lymphocytes, fibroblasts, or endothelial cells. Studies with different LfcinB-derived peptide fragments revealed that the cytotoxic activity of LfcinB resided within the amino acid sequence FKCRRWQWRM. Treatment of Jurkat T leukemia cells with LfcinB resulted in the production of reactive oxygen species followed by caspase-2-induced dissipation of mitochondrial transmembrane potential and subsequent activation of caspase-9 and caspase-3. Selective inhibitors of caspase-2 (Z-VDVAD-FMK), caspase-9 (Z-LEHD-FMK), and caspase-3 (Z-DEVD-FMK) protected both leukemia and carcinoma cells from LfcinB-induced apoptosis. Conversely, a caspase-8 inhibitor (Z-IETD-FMK) had no effect, which argued against a role for caspase-8 and was consistent with the finding that death receptors were not involved in LfcinB-induced apoptosis. Furthermore, Jurkat T leukemia cells that overexpressed Bcl-2 were less sensitive to LfcinB-induced apoptosis, which was characterized by mitochondrial swelling and the release of cytochrome c from mitochondria into the cytosolic compartment. We conclude that LfcinB kills cancer cells by triggering the mitochondrial pathway of apoptosis at least in part through the generation of reactive oxygen species.
authors.affiliation: Department of Pathology, Faculty of Medicine, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, Nova Scotia, Canada B3H 1X5.
authors.forename: Jamie S
authors.initials: JS
authors.lastname: Mader
authors.forename: Jayme
authors.initials: J
authors.lastname: Salsman
authors.forename: David M
authors.initials: DM
authors.lastname: Conrad
authors.forename: David W
authors.initials: DW
authors.lastname: Hoskin
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000737:chemistry; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis; D002277:Carcinoma / Q000188:drug therapy*; D053143:Caspase 2; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002417:Cattle; D045744:Cell Line, Tumor; D002470:Cell Survival; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000166:cytology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D019169:Jurkat Cells; D007781:Lactoferrin / Q000378:metabolism / Q000502:physiology*; D007938:Leukemia / Q000188:drug therapy*; D008214:Lymphocytes / Q000166:cytology; D008564:Membrane Potentials; D008854:Microscopy, Electron; D008928:Mitochondria / Q000378:metabolism / Q000473:pathology; D009842:Oligopeptides / Q000494:pharmacology; D010718:Phosphatidylserines / Q000737:chemistry; D017382:Reactive Oxygen Species; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D013997:Time Factors
chemical_list: D017304:Annexin A5; D000900:Anti-Bacterial Agents; D000975:Antioxidants; D004791:Enzyme Inhibitors; D009842:Oligopeptides; D010718:Phosphatidylserines; D017382:Reactive Oxygen Species; D013778:Tetrazolium Salts; D013844:Thiazoles; C110772:benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone; C427308:benzoylcarbonyl-valyl-aspartyl-valyl-alanyl-aspartyl-fluoromethyl ketone; C403753:benzyloxycarbonyl-isoleucyl-glutamyl-threonyl-aspartic acid fluoromethyl ketone; C403754:benzyloxycarbonyl-leucyl-glutamyl-histidyl-aspartic acid fluoromethyl ketone; C082171:lactoferricin B; D007781:Lactoferrin; C505407:CASP3 protein, human; C506433:CASP9 protein, human; D053143:Caspase 2; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases; C022616:thiazolyl blue