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: Ha-Na Kim, Do-Hee Kim, Eun-Hee Kim, Mee-Hyun Lee, Joydeb Kumar Kundu, Hye-Kyung Na, Young-Nam Cha, Young-Joon Surh
• Journal: Cancer letters (Cancer Lett) Vol. 351 Issue 1 Pg. 41-9 (Aug 28 2014) ISSN: 1872-7980 [Electronic] Ireland
• PMID: 24747121 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Chemical References

• Anticarcinogenic Agents
• Isothiocyanates
• NF-kappa B
• Sulfoxides
• Cyclooxygenase 2
• PTGS2 protein, human
• I-kappa B Kinase
• Extracellular Signal-Regulated MAP Kinases
• sulforaphane
• Tetradecanoylphorbol Acetate

Topics

• Anticarcinogenic Agents (pharmacology)
• Breast Neoplasms (prevention & control)
• Cell Line
• Cyclooxygenase 2 (genetics, metabolism)
• Drug Screening Assays, Antitumor
• Epithelial Cells (drug effects, enzymology)
• Extracellular Signal-Regulated MAP Kinases (metabolism)
• Female
• Gene Expression (drug effects)
• Humans
• I-kappa B Kinase (metabolism)
• Isothiocyanates (pharmacology)
• MAP Kinase Signaling System
• Mammary Glands, Human (pathology)
• NF-kappa B (metabolism)
• Phosphorylation
• Protein Binding
• Protein Processing, Post-Translational
• Sulfoxides
• Tetradecanoylphorbol Acetate (pharmacology)