title: Effector mechanisms of fenretinide-induced apoptosis in neuroblastoma.
abstract: Fenretinide is an effective inducer of apoptosis in many malignancies but its precise mechanism(s) of action in the induction of apoptosis in neuroblastoma is unclear. To characterize fenretinide-induced apoptosis, neuroblastoma cell lines were treated with fenretinide and flow cytometry was used to measure apoptosis, free radical generation, and mitochondrial permeability changes. Fenretinide induced high levels of caspase-dependent apoptosis accompanied by an increase in free radicals and the release of cytochrome c in the absence of mitochondrial permeability transition. Apoptosis was blocked by two retinoic acid receptor (RAR)-beta/gamma-specific antagonists, but not by an RARalpha-specific antagonist. Free radical induction in response to fenretinide was not blocked by the caspase inhibitor ZVAD or by RAR antagonists and was only marginally reduced in cells selected for resistance to fenretinide. Therefore, free radical generation may be only one of a number of intracellular mechanisms of apoptotic signaling in response to fenretinide. These results suggest that the effector pathway of fenretinide-induced apoptosis of neuroblastoma is caspase dependent, involving mitochondrial release of cytochrome c independently of permeability changes, and mediated by specific RARs. As the mechanism of action of fenretinide may be different from other retinoids, this compound may be a valuable adjunct to neuroblastoma therapy with retinoic acid and conventional chemotherapeutic drugs.
authors.affiliation: Department of Endocrinology, University of Newcastle upon Tyne, Newcastle upon Tyne, NE2 4HH, United Kingdom.
authors.forename: P E
authors.initials: PE
authors.lastname: Lovat
authors.forename: M
authors.initials: M
authors.lastname: Ranalli
authors.forename: M
authors.initials: M
authors.lastname: Annichiarrico-Petruzzelli
authors.forename: F
authors.initials: F
authors.lastname: Bernassola
authors.forename: M
authors.initials: M
authors.lastname: Piacentini
authors.forename: A J
authors.initials: AJ
authors.lastname: Malcolm
authors.forename: A D
authors.initials: AD
authors.lastname: Pearson
authors.forename: G
authors.initials: G
authors.lastname: Melino
authors.forename: C P
authors.initials: CP
authors.lastname: Redfern
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism; D017313:Fenretinide / Q000494:pharmacology*; D005609:Free Radicals / Q000378:metabolism; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009447:Neuroblastoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology*; D009842:Oligopeptides / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000037:antagonists & inhibitors; D014407:Tumor Cells, Cultured
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D000970:Antineoplastic Agents; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D003574:Cytochrome c Group; D005609:Free Radicals; D009842:Oligopeptides; D018168:Receptors, Retinoic Acid; C099158:acetyl-aspartyl-glutamyl-valyl-aspartal; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D017313:Fenretinide; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases