title: Role of Smad proteins in the regulation of NF-kappaB by TGF-beta in colon cancer cells.
abstract: Nuclear factor kappa B (NF-kappaB) has been implicated in cancer cell survival. We explored the role of the TGF-beta pathway in the regulation of NF-kappaB in colon cancer cells. TGF-beta-1 treatment of the colon adenocarcinoma cell line FET-1, results in an early increase in IkappaB-alpha phosphorylation that precedes NF-kappaB nuclear translocation and DNA binding activity. Activation of the TGF-beta type I receptor is required for the TGF-beta-mediated activation of NF-kappaB. No activation of NF-kappaB is observed in a Smad4 null cell line, SW480, even though TGF-beta does result in IkappaB-alpha phosphorylation in these cells. Smad4 restores the TGF-beta-1-mediated NF-kappaB activation in SW480 cells. TGF-beta-1 treatment fails to activate NF-kappaB or phosphorylate IkappaB-alpha in FET-1 cells expressing the inhibitory Smad, Smad7. Taken together, these results suggest a role for Smad4 in the transcriptional activation of NF-kappaB, and a direct effect of Smad 7 inhibiting IkappaB-alpha phosphorylation rather than through the well-established inhibition of Smad2/3 phosphorylation with subsequent inhibition of the TGF-beta pathway.
authors.affiliation: Department of Surgery, Meharry Medical College, 1005 Dr. D.B. Todd Jr. Blvd, Nashville, TN 37208, USA. agrau@mmc.edu
authors.forename: Ana M
authors.initials: AM
authors.lastname: Grau
authors.forename: Pran K
authors.initials: PK
authors.lastname: Datta
authors.forename: Jinghuan
authors.initials: J
authors.lastname: Zi
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Halder
authors.forename: R Daniel
authors.initials: RD
authors.lastname: Beauchamp
mesh_terms: D021581:Active Transport, Cell Nucleus; D030201:Activin Receptors, Type I / Q000378:metabolism; D000818:Animals; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D003110:Colonic Neoplasms; D004247:DNA / Q000378:metabolism; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D015398:Signal Transduction; D051901:Smad4 Protein / Q000502:physiology*; D051906:Smad7 Protein / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000502:physiology*; D053773:Transforming Growth Factor beta1
chemical_list: D016328:NF-kappa B; D018125:Receptors, Transforming Growth Factor beta; D051901:Smad4 Protein; D051906:Smad7 Protein; C508960:TGFB1 protein, human; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D004247:DNA; D017346:Protein Serine-Threonine Kinases; D051550:I-kappa B Kinase; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I