title: Akt-dependent NF-kappaB activation is required for bile acids to rescue colon cancer cells from stress-induced apoptosis.
abstract: Conjugated secondary bile acids promote human colon cancer cell proliferation by activating EGF receptors (EGFR). We hypothesized that bile acid-induced EGFR activation also mediates cell survival by downstream Akt-regulated activation of NF-kappaB. Deoxycholyltaurine (DCT) treatment attenuated TNF-alpha-induced colon cancer cell apoptosis, and stimulated rapid and sustained NF-kappaB nuclear translocation and transcriptional activity (detected by NF-kappaB binding to an oligonucleotide consensus sequence and by activation of luciferase reporter gene constructs). Both DCT-induced NF-kappaB nuclear translocation and attenuation of TNF-alpha-stimulated apoptosis were dependent on EGFR activation. Inhibitors of nuclear translocation, proteosome activity, and IkappaBalpha kinase attenuated NF-kappaB transcriptional activity. Cell transfection with adenoviral vectors encoding a non-degradable IkappaBalpha 'super-repressor' blocked the actions of DCT on both NF-kappaB activation and TNF-alpha-induced apoptosis. Likewise, transfection with mutant akt and treatment with a chemical inhibitor of Akt attenuated effects of DCT on NF-kappaB transcriptional activity and TNF-alpha-induced apoptosis. Chemical inhibitors of Akt and NF-kappaB activation also attenuated DCT-induced rescue of H508 cells from ultraviolet radiation-induced apoptosis. Collectively, these observations indicate that, downstream of EGFR, bile acid-induced colon cancer cell survival is mediated by Akt-dependent NF-kappaB activation. These findings provide a mechanism whereby bile acids increase resistance of colon cancer to chemotherapy and radiation.
authors.affiliation: Division of Gastroenterology and Hepatology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
authors.forename: Jasleen
authors.initials: J
authors.lastname: Shant
authors.forename: Kunrong
authors.initials: K
authors.lastname: Cheng
authors.forename: Bernard S
authors.initials: BS
authors.lastname: Marasa
authors.forename: Jian-Ying
authors.initials: JY
authors.lastname: Wang
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Raufman
mesh_terms: D021581:Active Transport, Cell Nucleus; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D001647:Bile Acids and Salts / Q000494:pharmacology; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002867:Chromones / Q000494:pharmacology; D003110:Colonic Neoplasms; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology; D009025:Morpholines / Q000494:pharmacology; D009154:Mutation; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D013450:Sulfones / Q000494:pharmacology; D013657:Taurodeoxycholic Acid / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: C434003:3-(4-methylphenylsulfonyl)-2-propenenitrile; D001647:Bile Acids and Salts; D002867:Chromones; D007976:Leupeptins; D009025:Morpholines; D016328:NF-kappa B; D009570:Nitriles; D010455:Peptides; C118258:SN50 peptide; D013450:Sulfones; D014409:Tumor Necrosis Factor-alpha; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D013657:Taurodeoxycholic Acid; C512478:EGFR protein, human; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D051550:I-kappa B Kinase; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde