An upstream CRE-E-box element is essential for gastrin-dependent activation of the cyclooxygenase-2 gene in human colon cancer cells.
Cyclooxygenase-2, the inducible enzyme of arachidonic acid metabolism and prostaglandin synthesis, is over expressed in colorectal cancer. Inhibition of COX-1/-2 by non-steroidal anti-inflammatory drugs is associated with a decreased risk for these malignancies, whereas high serum gastrin levels elevate this risk. As gastrin exhibits trophical effects on colonic epithelium we sought to explore whether it is capable to induce COX-2 expression in a human colon cancer cell line. The aim of this study is the description of the gastrin evoked effects on the transcriptional activity of the COX-2 gene in colorectal cancer cells and the identification of regulatory promoter elements. Reporter gene assays were performed with the gastrin-stimulated human colorectal cancer cell-line Colo-320, which was stable transfected with the human cholecystokinin-B/gastrin receptor cDNA and COX-2-promoter-luciferase constructs containing different segments of the 5'-region of the COX-2 gene or with mutated promoter constructs. Transcription factors were characterized with electrophoretic mobility shift assays. Gastrin-dependent induction of COX-2 mRNA was shown using "real-time" PCR. Resulting elevated Prostaglandin E2-levels were measured using ELISA. Gastrin stimulated the PGE2-generation and COX-2-mRNA expression in human Colo-320-B cells potently, obviously by transactivating the COX-2-promoter using a region between - 68 bp and + 70 bp. Further examinations identified a CRE-E-box element between - 56 bp and - 48 bp mediating the gastrin-effects on the COX-2 gene. Transcription factors binding to this promoter element were USF-1 und -2. These results show the necessity to perform succeeding studies, which could describe possible mechanisms in which gastrin and COX-2 contribute to the induction of colorectal carcinomas.
Ansorge
Nikolaus
N
Medizinische Klinik I, St. Josef-Hospital, Ruhr-Universität Bochum, Germany. n.ansorge@gmx.net
Jüttner
Stefan
S
Cramer
Thorsten
T
Schmidt
Wolfgang E
WE
Höcker
Michael
M
Schmitz
Frank
F
D001665:Binding Sites; D003110:Colonic Neoplasms / Q000201:enzymology / Q000235:genetics*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000235:genetics* / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism; D005755:Gastrins / Q000494:pharmacology*; D006801:Humans; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D020218:Response Elements; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D051720:Upstream Stimulatory Factors / Q000378:metabolism
D017362:Cyclic AMP Response Element-Binding Protein; D005755:Gastrins; D012333:RNA, Messenger; C497181:USF1 protein, human; C497184:USF2 protein, human; D051720:Upstream Stimulatory Factors; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D015232:Dinoprostone