title: Caspase-mediated p65 cleavage promotes TRAIL-induced apoptosis.
abstract: Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is cytotoxic to a wide variety of transformed cells, but not to most normal cells, implying potential therapeutic value against advanced cancer. However, signal transduction in TRAIL-mediated apoptosis is not clearly understood compared with other TNF family members. Specifically, it is not yet understood how TRAIL controls nuclear factor kappaB (NF-kappaB) activation and overcomes its anti-apoptotic effect. We explored the regulation of NF-kappaB activity by TRAIL and its role in apoptosis. TRAIL combined with IkappaBalpha-"superrepressor" induced potent apoptosis of SK-Hep1 hepatoma cells at low concentrations of TRAIL that do not independently induce apoptosis. Apoptosis by high concentrations of TRAIL was not affected by IkappaBalpha-superrepressor. Although TRAIL alone did not induce NF-kappaB activity, TRAIL combined with z-VAD significantly increased NF-kappaB activation. Analysis of the NF-kappaB activation pathway indicated that TRAIL unexpectedly induced cleavage of p65 at Asp97, which was blocked by z-VAD, accounting for all of these findings. p65 expression abrogated apoptosis and increased NF-kappaB activity in TRAIL-treated cells. Cleavage-resistant p65D97A further increased NF-kappaB activity in TRAIL-treated cells, whereas the COOH-terminal p65 fragment acted as a dominant-negative inhibitor. XIAP levels were increased by TRAIL in combination with z-VAD, whereas XIAP levels were decreased by TRAIL alone. Cleavage of p65 was also detected after FRO thyroid cancer cells were treated with TRAIL. These results suggest that TRAIL induces NF-kappaB activation, but simultaneously abrogates NF-kappaB activation by cleaving p65, and thereby inhibits the induction of anti-apoptotic proteins such as XIAP, which contributes to the strong apoptotic activity of TRAIL compared with other TNF family members.
authors: Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Kangnam-ku, Seoul, Korea.
authors: Hun Sik
authors: HS
authors: Kim
authors: Inik
authors: I
authors: Chang
authors: Ja Young
authors: JY
authors: Kim
authors: Kyung-Hee
authors: KH
authors: Choi
authors: Myung-Shik
authors: MS
authors: Lee
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D051017:Apoptosis Regulatory Proteins; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand; D051996:Transcription Factor RelA; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D051636:X-Linked Inhibitor of Apoptosis Protein
chemical_list: D051017:Apoptosis Regulatory Proteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D011506:Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases