title: Sulforaphane inhibits phorbol ester-stimulated IKK-NF-κB signaling and COX-2 expression in human mammary epithelial cells by targeting NF-κB activating kinase and ERK.
abstract: Sulforaphane, an isothiocyanate present in cruciferous vegetables, has been reported to possess anti-inflammatory and cancer chemopreventive properties. However, the molecular mechanisms by which sulforaphane suppresses inflammation and carcinogenesis are yet to be fully elucidated. Since the aberrant expression of cyclooxygenase-2 (COX-2) links inflammation and cancer, the present study was aimed to elucidate the mechanisms by which sulforaphane modulates COX-2 overexpression in human mammary epithelial (MCF-10A) cells stimulated with a prototypic tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Treatment of MCF-10A cells with sulforaphane significantly inhibited TPA-induced expression of COX-2 protein and its mRNA transcript. Transient transfection of cells with deletion mutant constructs of COX-2 promoter revealed that the transcription factor nuclear factor-kappaB (NF-κB) plays a key role in TPA-induced COX-2 expression in MCF-10A cells. Pretreatment with sulforaphane significantly attenuated nuclear localization, DNA binding and the transcriptional activity of NF-κB through inhibition of phosphorylation and subsequent degradation of IκBα in MCF-10A cells stimulated with TPA. Sulforaphane also attenuated TPA-induced activation of IκB kinases (IKK), NF-κB-activating kinase (NAK) and extracellular signal-regulated kinase-1/2 (ERK1/2). Pharmacological inhibition of IKK or transient transfection of cells with dominant-negative mutant forms of this kinase abrogated TPA-induced NF-κB activation and COX-2 expression. In addition, the blockade of ERK1/2 activation negated the catalytic activity of IKKα, but not that of IKKβ, whereas silencing NAK by specific siRNA abrogated the IKKβ activity in TPA-treated cells. Taken together, sulforaphane inhibits TPA-induced NF-κB activation and COX-2 expression in MCF-10A cells by blocking two distinct signaling pathways mediated by ERK1/2-IKKα and NAK-IKKβ.
authors.affiliation: Research Institute for Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, South Korea.
authors.forename: Ha-Na
authors.initials: HN
authors.lastname: Kim
authors.affiliation: Research Institute for Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, South Korea.
authors.forename: Do-Hee
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Research Institute for Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, South Korea.
authors.forename: Eun-Hee
authors.initials: EH
authors.lastname: Kim
authors.affiliation: Research Institute for Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, South Korea.
authors.forename: Mee-Hyun
authors.initials: MH
authors.lastname: Lee
authors.affiliation: College of Pharmacy, Keimyung University, Daegu 704-701, South Korea.
authors.forename: Joydeb Kumar
authors.initials: JK
authors.lastname: Kundu
authors.affiliation: Department of Food and Nutrition, Sungshin Women's University, Seoul 136-742, South Korea.
authors.forename: Hye-Kyung
authors.initials: HK
authors.lastname: Na
authors.affiliation: College of Medicine, Inha University, Incheon, South Korea.
authors.forename: Young-Nam
authors.initials: YN
authors.lastname: Cha
authors.affiliation: Research Institute for Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul 151-742, South Korea; Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 151-742, South Korea; Cancer Research Institute, Seoul National University, Seoul, South Korea. Electronic address: surh@plaza.snu.ac.kr.
authors.forename: Young-Joon
authors.initials: YJ
authors.lastname: Surh
mesh_terms: D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000517:prevention & control; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D004354:Drug Screening Assays, Antitumor; D004847:Epithelial Cells / Q000187:drug effects* / Q000201:enzymology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism*; D017879:Isothiocyanates / Q000494:pharmacology*; D020935:MAP Kinase Signaling System; D042361:Mammary Glands, Human / Q000473:pathology; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D013454:Sulfoxides; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D016588:Anticarcinogenic Agents; D017879:Isothiocyanates; D016328:NF-kappa B; D013454:Sulfoxides; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D051550:I-kappa B Kinase; D048049:Extracellular Signal-Regulated MAP Kinases; C016766:sulforaphane; D013755:Tetradecanoylphorbol Acetate
keywords: Chemoprevention; Cyclooxygenase-2; IkappaB kinase; NF-κB-activating kinase; Sulforaphane