title: Type 3 repeat/C-terminal domain of thrombospondin-1 triggers caspase-independent cell death through CD47/alphavbeta3 in promyelocytic leukemia NB4 cells.
abstract: By means of its antiangiogenic activity, thrombospondin-1 (TSP-1) exerts indirect antitumoral action on solid tumors. Here, we investigated potential antitumor action in an in vitro cell model for promyelocytic leukemia (NB4-LR1), resistant to retinoid maturation. Purified soluble TSP-1 added to cultures induced a strong dose-dependent growth inhibition and a slowly developing maturation-independent cell death. Recombinant fragments of TSP-1 allowed mapping of these activities to its type 3 repeat/C-terminal domain, features that are distinct from those of TSP-1 action on solid tumors, previously ascribed to the type 1 repeat domain. Cell death in leukemia was characterized as a caspase-independent mechanism, without DNA fragmentation, but phosphatidylserine externalization followed by membrane permeabilization. Mitochondria membrane depolarization was inherent to TSP-1 action but did not produce release of death-promoting proteins (eg, noncaspase apoptosis regulators, apoptosis-induced factor [AIF], endonuclease G, or Omi/HtrA2 or the caspase regulators, cytochrome c or second mitochondrial activator of caspase/direct inhibitor of apoptosis protein-binding protein with low isoelectric point [Smac/DIABLO]). Although detected, reactive oxygen species (ROS) production was likely not involved in the death process. Finally, receptor agonist RFYVVM and RGD peptides indicated that TSP-1 death effects are mediated by membrane receptors CD47 and alphavbeta3. These results demonstrated a new domain-specific antitumoral activity of TSP-1 on a leukemia cell line, which extends TSP-1 therapeutic potential outside the area of vascularized solid tumors.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, INSERM U-685, Paris, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Saumet
authors.forename: Mouna Ben
authors.initials: MB
authors.lastname: Slimane
authors.forename: Michel
authors.initials: M
authors.lastname: Lanotte
authors.forename: Jack
authors.initials: J
authors.lastname: Lawler
authors.forename: Véronique
authors.initials: V
authors.lastname: Dubernard
mesh_terms: D000595:Amino Acid Sequence; D015703:Antigens, CD / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D001483:Base Sequence; D051928:CD47 Antigen; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000378:metabolism; D015473:Leukemia, Promyelocytic, Acute / Q000188:drug therapy* / Q000276:immunology / Q000473:pathology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D017382:Reactive Oxygen Species / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D019700:Thrombospondin 1 / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D014212:Tretinoin / Q000494:pharmacology
chemical_list: D015703:Antigens, CD; D051928:CD47 Antigen; C497894:CD47 protein, human; D039302:Integrin alphaVbeta3; D010446:Peptide Fragments; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins; D019700:Thrombospondin 1; D014212:Tretinoin; D020169:Caspases