title: Effect of the XIAP inhibitor Embelin on TRAIL-induced apoptosis of pancreatic cancer cells.
abstract: BACKGROUND
  Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potent inducer of apoptosis in a wide variety of tumor cells, while it has no toxicity for the majority of normal cells.Therefore, TRAIL may be a suitable agent for anticancer therapy. We previously reported that a number of pancreatic cancer cell lines show resistance to TRAIL-induced apoptosis via overexpression of XIAP and FLIP. The present study was conducted to further examine TRAIL-based therapeutic strategies by aiming to restore functional apoptotic pathways in resistant pancreatic cancer cells.
  
  
  METHODS
  In various pancreatic cancer cell lines, TRAIL-induced apoptosis was evaluated in the presence or absence of an XIAP-inhibitor (Smac peptide). Second, TRAIL-induced apoptosis was evaluated in TRAIL-resistant AsPC-1 cells with or without FLIP antisense. Third, the combined effect of Smac peptide and FLIP antisense was tested, and the activation of apoptosis-related caspases and poly (ADP-ribose) polymerase was evaluated. Finally, TRAIL-induced apoptosis was evaluated in the presence or absence of FLIP antisense and an XIAP inhibitor (embelin).
  
  
  RESULTS
  Smac peptide enhanced TRAIL-induced apoptosis in a dose-dependent manner for several pancreatic cancer cell lines, but showed no effect on TRAIL-resistant AsPC-1 cells. Smac peptide alone had no influence on cell viability. TRAIL-induced apoptosis was restored in TRAIL-resistant AsPC-1 cells by exposure to FLIP antisense, which suppressed the expression of FLIP. The effect of TRAIL was augmented by the combination of FLIP antisense and Smac peptide. Similarly, TRAIL-induced apoptosis was restored by the combination of FLIP antisense and embelin. Activation of apoptotic caspases and cleavage of poly (ADP-ribose) polymerase was observed after sensitization of TRAIL-resistant pancreatic cancer cells.
  
  
  CONCLUSIONS
  Pancreatic cancer cells gain resistance to TRAIL-induced apoptosis via expression of the antiapoptotic proteins XIAP and FLIP. Smac peptide and FLIP antisense could restore the apoptotic effect of TRAIL. An XIAP inhibitor, embelin, enhanced the effect of TRAIL in the presence of FLIP antisense. These findings may provide useful information for the development of TRAIL-based therapeutic strategies by restoring functional apoptotic pathways in resistant pancreatic cancer cells. In addition, a low molecular weight XIAP inhibitor like embelin could be a lead compound for the development of effective XIAP inhibitors.
authors.affiliation: Department of Surgery, Division of Hepato-Biliary-Pancreatic Surgery and Transplantation, Kyoto University, Kyoto, Japan.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Mori
authors.forename: Ryuichiro
authors.initials: R
authors.lastname: Doi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kida
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Nagai
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kami
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ito
authors.forename: Eiji
authors.initials: E
authors.lastname: Toyoda
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Kawaguchi
authors.forename: Shinji
authors.initials: S
authors.lastname: Uemoto
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D051017:Apoptosis Regulatory Proteins; D016227:Benzoquinones / Q000494:pharmacology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000037:antagonists & inhibitors / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D004347:Drug Interactions; D004357:Drug Synergism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology*; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000037:antagonists & inhibitors*
chemical_list: D051017:Apoptosis Regulatory Proteins; D016227:Benzoquinones; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C412403:DIABLO protein, human; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D010446:Peptide Fragments; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases; C010945:embelin