title: Proteasome inhibitors sensitize colon carcinoma cells to TRAIL-induced apoptosis via enhanced release of Smac/DIABLO from the mitochondria.
abstract: The synergistic interaction between proteasome inhibitors and tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a promising approach to induce cell death in tumor cells. However, the molecular and biochemical mechanisms of this synergism have been proven to be cell type specific. We therefore focused our investigation on TRAIL-resistant colon carcinoma cells in this study. DNA fragmentation, mitochondrial membrane depolarization and increased caspase-3-like enzyme activity was exclusively induced only by combined treatment with proteasome inhibitors (epoxomicin, MG132, bortezomib/PS-341) and TRAIL. The expression level of anti-apoptotic proteins (XIAP, survivin, Bcl-2, Bcl-XL), regulated by NF-kappaB transcription factor, was not effected by any of these treatments. TRAIL alone induced only partial activation of caspase-3 (p20), while the combination of TRAIL and proteasome inhibition led to the full proteolytic activation of caspase-3 (p17). Only the combination treatment induced marked membrane depolarization and the release of cytochrome c, HtrA2/Omi and Smac/DIABLO. Apoptosis-inducing factor (AIF) was not released in any of these conditions. These results are consistent with a model where the full activation of caspase-3 by caspase-8 is dependent on the release of Smac/DIABLO in response to the combined treatment. This molecular mechanism, independent of the inhibition NF-kappaB activity, may provide rationale for the combination treatment of colon carcinomas with proteasome inhibitors and recombinant TRAIL or agonistic antibody of TRAIL receptors.
authors.affiliation: Ist Department of Pathology and Experimental Cancer Research, Semmelweis University, Budapest, Hungary.
authors.forename: Katalin
authors.initials: K
authors.lastname: Nagy
authors.forename: Kinga
authors.initials: K
authors.lastname: Székely-Szüts
authors.forename: Kamel
authors.initials: K
authors.lastname: Izeradjene
authors.forename: Leslie
authors.initials: L
authors.lastname: Douglas
authors.forename: Mike
authors.initials: M
authors.lastname: Tillman
authors.forename: Helga
authors.initials: H
authors.lastname: Barti-Juhász
authors.forename: Massimo
authors.initials: M
authors.lastname: Dominici
authors.forename: Carlotta
authors.initials: C
authors.lastname: Spano
authors.forename: Gian
authors.initials: G
authors.lastname: Luca Cervo
authors.forename: Pierfranco
authors.initials: P
authors.lastname: Conte
authors.forename: Janet A
authors.initials: JA
authors.lastname: Houghton
authors.forename: Rudolf
authors.initials: R
authors.lastname: Mihalik
authors.forename: László
authors.initials: L
authors.lastname: Kopper
authors.forename: István
authors.initials: I
authors.lastname: Peták
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D004357:Drug Synergism; D004789:Enzyme Activation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D007976:Leupeptins / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology*; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000494:pharmacology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D001897:Boronic Acids; C412403:DIABLO protein, human; D047908:Intracellular Signaling Peptides and Proteins; D007976:Leupeptins; D024101:Mitochondrial Proteins; D009842:Oligopeptides; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011719:Pyrazines; D053221:TNF-Related Apoptosis-Inducing Ligand; D000069286:Bortezomib; D053148:Caspase 3; D053181:Caspase 8; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; C078846:epoxomicin