title: Bortezomib sensitizes human renal cell carcinomas to TRAIL apoptosis through increased activation of caspase-8 in the death-inducing signaling complex.
abstract: Bortezomib (VELCADE) could sensitize certain human renal cell carcinoma (RCC) lines to the apoptotic effects of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Analysis of seven human RCC showed a clear increase in the sensitivity of four of the RCC to TRAIL cytotoxicity following bortezomib (5-20 nmol/L) treatment, whereas the remaining three remained resistant. Tumor cell death following sensitization had all the features of apoptosis. The enhanced antitumor activity of the bortezomib and TRAIL combination was confirmed in long-term (6 days) cancer cell outgrowth assays. The extent of proteasome inhibition by bortezomib in the various RCC was equivalent. Following bortezomib treatment, neither changes in the intracellular protein levels of various Bcl-2 and IAP family members, nor minor changes in expression of TRAIL receptors (DR4, DR5), correlated well with the sensitization or resistance of RCC to TRAIL-mediated apoptosis. However, enhanced procaspase-8 activation following bortezomib pretreatment and subsequent TRAIL exposure was only observed in the sensitized RCC in both cell extracts and death-inducing signaling complex immunoprecipitates. These data suggest that the molecular basis for bortezomib sensitization of RCC to TRAIL primarily involves early amplification of caspase-8 activity. In the absence of this increased caspase-8 activation, other bortezomib-induced changes are not sufficient to sensitize RCC to TRAIL-mediated apoptosis.
authors.affiliation: Science Applications International Corporation-Frederick, Inc., MD, USA.
authors.forename: Alan D
authors.initials: AD
authors.lastname: Brooks
authors.forename: Kristen M
authors.initials: KM
authors.lastname: Jacobsen
authors.forename: Wenqing
authors.initials: W
authors.lastname: Li
authors.forename: Anil
authors.initials: A
authors.lastname: Shanker
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Sayers
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001897:Boronic Acids / Q000494:pharmacology* / Q000627:therapeutic use; D000069286:Bortezomib; D002292:Carcinoma, Renal Cell / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology*; D053181:Caspase 8 / Q000378:metabolism*; D045744:Cell Line, Tumor; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007680:Kidney Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology*; D011719:Pyrazines / Q000494:pharmacology* / Q000627:therapeutic use; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000502:physiology*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: D000970:Antineoplastic Agents; D001897:Boronic Acids; D053418:Death Domain Receptor Signaling Adaptor Proteins; D011719:Pyrazines; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D000069286:Bortezomib; D053181:Caspase 8