title: Epidermal growth factor stimulates nuclear factor-κB activation and heme oxygenase-1 expression via c-Src, NADPH oxidase, PI3K, and Akt in human colon cancer cells.
abstract: Previous report showed that epidermal growth factor (EGF) promotes tumor progression. Several studies demonstrated that growth factors can induce heme oxygenase (HO)-1 expression, protect against cellular injury and cancer cell proliferation. In this study, we investigated the involvement of the c-Src, NADPH oxidase, reactive oxygen species (ROS), PI3K/Akt, and NF-κB signaling pathways in EGF-induced HO-1 expression in human HT-29 colon cancer cells. Treatment of HT-29 cells with EGF caused HO-1 to be expressed in concentration- and time-dependent manners. Treatment of HT-29 cells with AG1478 (an EGF receptor (EGFR) inhibitor), small interfering RNA of EGFR (EGFR siRNA), a dominant negative mutant of c-Src (c-Src DN), DPI (an NADPH oxidase inhibitor), glutathione (an ROS inhibitor), LY294002 (a PI3K inhibitor), and an Akt DN inhibited EGF-induced HO-1 expression. Stimulation of cells with EGF caused an increase in c-Src phosphorylation at Tyr406 in a time-dependent manner. Treatment of HT-29 cells with EGF induced an increase in p47(phox) translocation from the cytosol to membranes. The EGF-induced ROS production was inhibited by DPI. Stimulation of cells with EGF resulted in an increase in Akt phosphorylation at Ser473, which was inhibited by c-Src DN, DPI, and LY 294002. Moreover, treatment of HT-29 cells with a dominant negative mutant of IκB (IκBαM) inhibited EGF-induced HO-1 expression. Stimulation of cells with EGF induced p65 translocation from the cytosol to nuclei. Treatment of HT-29 cells with EGF induced an increase in κB-luciferase activity, which was inhibited by a c-Src DN, LY 294002, and an Akt DN. Furthermore, EGF-induced colon cancer cell proliferation was inhibited by Sn(IV)protoporphyrin-IX (snPP, an HO-1 inhibitor). Taken together, these results suggest that the c-Src, NADPH oxidase, PI3K, and Akt signaling pathways play important roles in EGF-induced NF-κB activation and HO-1 expression in HT-29 cells. Moreover, overexpression of HO-1 mediates EGF-induced colon cancer cell proliferation.
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
authors.forename: Gi-Shih
authors.initials: GS
authors.lastname: Lien
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan; Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Ming-Shun
authors.initials: MS
authors.lastname: Wu
authors.affiliation: School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan; Division of Pulmonary Medicine, Department of Internal Medicine, Taipei Medical University Hospital, Taipei, Taiwan.
authors.forename: Mauo-Ying
authors.initials: MY
authors.lastname: Bien
authors.affiliation: Division of Colorectal Surgery, Department of Surgery, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
authors.forename: Chien-Hsin
authors.initials: CH
authors.lastname: Chen
authors.affiliation: Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Chien-Huang
authors.initials: CH
authors.lastname: Lin
authors.affiliation: School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Bing-Chang
authors.initials: BC
authors.lastname: Chen
mesh_terms: D001483:Base Sequence; D003110:Colonic Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D017931:DNA Primers; D004815:Epidermal Growth Factor / Q000502:physiology*; D019073:HT29 Cells; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D006801:Humans; D019255:NADPH Oxidases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D016133:Polymerase Chain Reaction; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism
chemical_list: D017931:DNA Primers; D016328:NF-kappa B; D004815:Epidermal Growth Factor; D051547:Heme Oxygenase-1; D019255:NADPH Oxidases; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D016283:Proto-Oncogene Proteins p21(ras)