Proteasome inhibitors sensitize colon carcinoma cells to TRAIL-induced apoptosis via enhanced release of Smac/DIABLO from the mitochondria.
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.
Nagy
Katalin
K
Ist Department of Pathology and Experimental Cancer Research, Semmelweis University, Budapest, Hungary.
Székely-Szüts
Kinga
K
Izeradjene
Kamel
K
Douglas
Leslie
L
Tillman
Mike
M
Barti-Juhász
Helga
H
Dominici
Massimo
M
Spano
Carlotta
C
Luca Cervo
Gian
G
Conte
Pierfranco
P
Houghton
Janet A
JA
Mihalik
Rudolf
R
Kopper
László
L
Peták
István
I
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*
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