Levels of cyclooxygenase-2 are increased in the oral mucosa of smokers: evidence for the role of epidermal growth factor receptor and its ligands.
Cyclooxygenase-2 (COX-2) is a promising pharmacologic target for preventing aerodigestive malignancies. In this study, we investigated the effects of tobacco smoke on the expression of COX-2 in oral mucosa. An approximately 4-fold increase in amount of COX-2 mRNA was observed in the oral mucosa of active smokers versus never smokers. Thus, a series of in vitro studies were carried out to elucidate the mechanism by which tobacco smoke induced COX-2. Treatment of a nontumorigenic oral epithelial cell line (MSK-Leuk1) with a saline extract of tobacco smoke (TS) stimulated COX-2 transcription, resulting in increased amounts of COX-2 mRNA, COX-2 protein, and prostaglandin E(2) (PGE(2)) synthesis. Exposure of cells to TS also caused an increase in epidermal growth factor receptor (EGFR) tyrosine kinase activity. Both an inhibitor of EGFR tyrosine kinase activity and a neutralizing anti-EGFR antibody blocked TS-mediated induction of COX-2. To define the mechanism by which TS activated EGFR, the release of amphiregulin and transforming growth factor alpha, two ligands of the EGFR, was measured. Exposure to TS caused a rapid increase in the release of both ligands. TS also markedly induced the expression of mRNAs for amphiregulin and transforming growth factor alpha. Importantly, increased expression of both ligands was also detected in the oral mucosa of active smokers. Taken together, these results suggest that activation of EGFR signaling contributes to the elevated levels of COX-2 found in the oral mucosa of smokers. Moreover, these findings strengthen the rationale for determining whether inhibitors of COX-2 or EGFR tyrosine kinase activity can reduce the risk of tobacco smoke-related malignancies of the aerodigestive tract.
Moraitis
Dimitrios
D
Head and Neck Service, Department of Surgery, Memorial Sloan-Kettering Cancer Center, Weill Medical College of Cornell University, New York, NY 10021, USA.
Du
Baoheng
B
De Lorenzo
Mariana S
MS
Boyle
Jay O
JO
Weksler
Babette B
BB
Cohen
Erik G
EG
Carew
John F
JF
Altorki
Nasser K
NK
Kopelovich
Levy
L
Subbaramaiah
Kotha
K
Dannenberg
Andrew J
AJ
D015152:Blotting, Northern; D051546:Cyclooxygenase 2; D066246:ErbB Receptors / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D008565:Membrane Proteins; D009061:Mouth Mucosa / Q000201:enzymology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012907:Smoking / Q000378:metabolism*
D008024:Ligands; D008565:Membrane Proteins; D012333:RNA, Messenger; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D066246:ErbB Receptors