title: Sulindac metabolites induce caspase- and proteasome-dependent degradation of beta-catenin protein in human colon cancer cells.
abstract: Colorectal cancer (CRC) is the second leading cause of cancer death in the USA. Accumulation of beta-catenin protein is nearly ubiquitous in colon adenomas and cancers, presumably due to mutations in the APC or beta-catenin genes that inhibit proteasome-dependent degradation of beta-catenin protein. Substantial clinical, epidemiological, and animal evidence indicate that sulindac and other non-steroidal anti-inflammatory drugs (NSAIDs) prevent the development of CRC. The mechanisms by which sulindac exerts its potent growth inhibitory effects against colon tumor cells are incompletely understood, but down-regulation of beta-catenin has been suggested as one potential mechanism. The goal of this study was to determine the mechanism of beta-catenin protein down-regulation by sulindac metabolites. Treatment of human colon cancer cell lines with apoptotic concentrations of sulindac metabolites (sulindac sulfide, sulindac sulfone) induced a dose- and time-dependent inhibition of beta-catenin protein expression. Inhibition of proteasome activity with MG-132 partially blocked the ability of sulindac sulfide and sulindac sulfone to inhibit beta-catenin protein expression. Pretreatment with the caspase inhibitor z-VAD-fmk blocked morphological signs of apoptosis as well as caspase cleavage, and also partially prevented beta-catenin degradation by sulindac metabolites. These effects occurred in cells with bi-allelic APC mutation (SW480), with wild-type APC but mono-allelic beta-catenin mutation (HCT116) and in cells that lack expression of either COX-1 or -2 (HCT15). These results indicate that loss of beta-catenin protein induced by sulindac metabolites is COX independent and at least partially due to reactivation of beta-catenin proteasome degradation and partially a result of caspase activation during the process of apoptosis.
authors.affiliation: Department of Medicine, University of Colorado Health Sciences Center, Denver, CO 80262, USA. pamela.rice@uchsc.edu
authors.forename: Pamela L
authors.initials: PL
authors.lastname: Rice
authors.forename: Jennifer
authors.initials: J
authors.lastname: Kelloff
authors.forename: Holly
authors.initials: H
authors.lastname: Sullivan
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Driggers
authors.forename: K Scott
authors.initials: KS
authors.lastname: Beard
authors.forename: Scott
authors.initials: S
authors.lastname: Kuwada
authors.forename: Gary
authors.initials: G
authors.lastname: Piazza
authors.forename: Dennis J
authors.initials: DJ
authors.lastname: Ahnen
mesh_terms: D011125:Adenomatous Polyposis Coli / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000473:pathology; D003546:Cysteine Endopeptidases / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D015398:Signal Transduction; D013467:Sulindac / Q000031:analogs & derivatives* / Q000494:pharmacology*; D015534:Trans-Activators / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D051176:beta Catenin
chemical_list: D000970:Antineoplastic Agents; C495270:CTNNB1 protein, human; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D003598:Cytoskeletal Proteins; D004791:Enzyme Inhibitors; D007976:Leupeptins; D009097:Multienzyme Complexes; D015534:Trans-Activators; D051176:beta Catenin; D013467:Sulindac; C025462:sulindac sulfide; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C025463:sulindac sulfone; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde