Triptolide and TRAIL combination enhances apoptosis in cholangiocarcinoma.
BACKGROUND
Cholangiocarcinoma originates from bile duct epithelial cells in the intrahepatic and extrahepatic biliary system. We recently observed that triptolide (a diterpenoid triepoxide) is effective in inducing apoptosis in pancreatic tumors. Death receptors 4 and 5 are overexpressed in several cancer types, and their activation by tumor-necrosis factor-related apoptosis-inducing ligand (TRAIL) induces cell death. The principal objective of this study was to determine the effects of combination therapy with TRAIL and triptolide in cholangiocarcinoma.


METHODS
Two cholangiocarcinoma cell lines were incubated with various doses of triptolide and TRAIL, alone and in combination; cell viability was assessed at 24 and 48 h. Annexin-V staining and caspase-3 activity were measured after 24 h of triptolide, TRAIL or combination treatment. Western blots assessed protein levels of poly(ADP-ribose) polymerase (PARP) and X-linked inhibitor of apoptosis (XIAP).


RESULTS
Combination treatment using TRAIL and triptolide decreased cell viability in all cell lines at 48 h, with greater cell killing than that which was observed with either drug alone. This decrease in viability was associated with increases in annexin-V staining and caspase-3 activity. Western blot analysis demonstrated increases in PARP cleavage and decreases in XIAP expression that were dose-dependent.


CONCLUSIONS
TRAIL and triptolide in combination decreased cell viability and enhanced apoptosis. Furthermore, Western blot analysis suggests that triptolide sensitizes cells to TRAIL-induced apoptotic cell death by inhibiting expression of XIAP, a protein known to inhibit apoptosis. Our results demonstrate that combination of TRAIL and triptolide enhance apoptosis in cholangiocarcinoma cell lines.
Clawson
Kimberly A
KA
Department of Surgery, Division of Basic and Translational Research, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Borja-Cacho
Daniel
D
Antonoff
Mara B
MB
Saluja
Ashok K
AK
Vickers
Selwyn M
SM
D017304:Annexin A5 / Q000032:analysis; D017209:Apoptosis / Q000187:drug effects*; D001650:Bile Duct Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D001653:Bile Ducts, Intrahepatic; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D018281:Cholangiocarcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D004224:Diterpenes / Q000494:pharmacology*; D004357:Drug Synergism; D004852:Epoxy Compounds / Q000494:pharmacology; D006801:Humans; D010616:Phenanthrenes / Q000494:pharmacology*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism
D017304:Annexin A5; D004224:Diterpenes; D004852:Epoxy Compounds; D010616:Phenanthrenes; D053221:TNF-Related Apoptosis-Inducing Ligand; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; C001899:triptolide; D011065:Poly(ADP-ribose) Polymerases; D053148:Caspase 3