title: Roles of ERK and p38 mitogen-activated protein kinases in phorbol ester-induced NF-kappaB activation and COX-2 expression in human breast epithelial cells.
abstract: Inappropriate up-regulation of cyclooxygenase-2 (COX-2) has been implicated in pathogenesis of various types of human cancer. Thus, COX-2 has been recognized as an important target for the chemoprevention of several human malignancies including breast cancer. COX-2 expression is known to be regulated by the eukaryotic transcription factor NF-kappaB. In an attempt to link the NF-kappaB activation and COX-2 induction during mammary carcinogenesis, we have examined the effects of 12-O-tetradecanoylphorbol-13-acetate (TPA), a prototype tumor promoter and a mitogen, on NF-kappaB activation and COX-2 expression in the immortalized human breast epithelial cell line (MCF10A). Treatment of MCF10A cells with TPA resulted in transient induction of NF-kappaB DNA binding with maximal activation observed at 30 min. Increased DNA binding of NF-kappaB was accompanied by enhancement of its transcriptional activity as determined by the luciferase reporter gene assay. Under the same experimental conditions, expression of COX-2 mRNA and its protein product peaked at 2h and 4h, respectively. TPA treatment caused an increase in the production of prostaglandin E(2). Treatment of cells with the NF-kappaB inhibitor pyrrolidine dithiocarbamate resulted in significant suppression of TPA-induced COX-2 expression. TPA induced activation of ERK1/2 and p38 mitogen-activated protein kinases (MAPK) via phosphorylation. PD98059 (ERK inhibitor) and SB203580 (p38 MAPK inhibitor) down-regulated the COX-2 expression induced by TPA. Furthermore, TPA-induced COX-2 induction as well as NF-kappaB activation was blocked in MCF10A cells transfected with dominant negative mutant ERK1/2 or p38 MAPK. These results suggest that both p38 and ERK MAPKs activates NF-kappaB signaling, which in turn induces COX-2 expression in TPA-stimulated human mammary epithelial cells.
authors.affiliation: National Research Laboratory of Molecular Carcinogenesis and Chemoprevention, College of Pharmacy, Seoul National University, Seoul 151-742, South Korea.
authors.forename: Jung-Hwan
authors.initials: JH
authors.lastname: Kim
authors.forename: Hye-Kyung
authors.initials: HK
authors.lastname: Na
authors.forename: Youngmi K
authors.initials: YK
authors.lastname: Pak
authors.forename: Yun-Sil
authors.initials: YS
authors.lastname: Lee
authors.forename: Su-Jae
authors.initials: SJ
authors.lastname: Lee
authors.forename: Aree
authors.initials: A
authors.lastname: Moon
authors.forename: Young-Joon
authors.initials: YJ
authors.lastname: Surh
mesh_terms: D015152:Blotting, Northern; D015153:Blotting, Western; D001940:Breast / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D045744:Cell Line, Tumor; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D016328:NF-kappa B; D012333:RNA, Messenger; D051546:Cyclooxygenase 2; D020928:Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate