Transcriptional regulation of cyclooxygenase-2 in mouse skin carcinoma cells. Regulatory role of CCAAT/enhancer-binding proteins in the differential expression of cyclooxygenase-2 in normal and neoplastic tissues.
Many studies have suggested that overexpression of cyclooxygenase-2 (COX-2) contributes to the development of tumors in several tissues. COX-2 expression tends to be up-regulated in various types of tumors and transformed cell lines, and the overexpression of COX-2 is caused by enhanced transcription of the gene. In an attempt to characterize the signaling pathway leading to the overexpression of COX-2 in the mouse skin carcinoma cell line JWF2, we investigated cis- and trans-acting factors required for COX-2 expression and demonstrated a molecular mechanism by which COX-2 is expressed differentially in normal and neoplastic tissues. Two regions of the COX-2 promoter containing an E-box and nuclear factor IL6 site were identified as the positive regulatory elements through transient transfections with luciferase reporter vectors containing the various 5'-flanking regions of the promoter. Moreover, electrophoretic mobility shift assays and cotransfection experiments showed that upstream stimulatory factors and CCAAT/enhancer-binding proteins (C/EBPs) bind to the E-box and nuclear factor IL6 site, respectively, and functionally transactivate the COX-2 promoter. We also found that C/EBP isoforms are expressed differentially during mouse skin carcinogenesis, suggesting that overexpression of COX-2 in tumors may be caused by a change in C/EBP expression levels.
Department of Carcinogenesis, University of Texas, M. D. Anderson Cancer Center, Science Park-Research Division, Smithville, Texas 78957, USA.
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Kim
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Fischer
D051696:Activating Transcription Factors; D000818:Animals; D001798:Blood Proteins / Q000378:metabolism; D022762:CCAAT-Enhancer-Binding Proteins; D002294:Carcinoma, Squamous Cell / Q000201:enzymology / Q000235:genetics*; D000242:Cyclic AMP / Q000378:metabolism; D051546:Cyclooxygenase 2; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis / Q000235:genetics*; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D012878:Skin Neoplasms / Q000201:enzymology / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D051720:Upstream Stimulatory Factors
D051696:Activating Transcription Factors; D001798:Blood Proteins; D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D007527:Isoenzymes; D009687:Nuclear Proteins; D020033:Protein Isoforms; D014157:Transcription Factors; D051720:Upstream Stimulatory Factors; D000242:Cyclic AMP; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases