Gastrin and EGF synergistically induce cyclooxygenase-2 expression in Swiss 3T3 fibroblasts that express the CCK2 receptor.
Over-expression of cyclooxygenase-2 (COX-2) has been demonstrated to be tumorigenic in transgenic mice. Chronic treatment with NSAIDs is chemoprotective for colorectal cancer. Gastrin is a growth factor for gastric mucosa and has been shown to promote proliferation of colorectal cells. Recent studies suggest that COX-2 expression levels could mediate the growth effects of gastrin. Here, we report that gastrin increased PGE2 secretion in Swiss 3T3 cells expressing the CCK2 receptor. Gastrin dose dependently induced COX-2 protein levels in a time dependent manner. COX-2 mRNA levels were rapidly induced by a dose dependent increase in gastrin. Prior treatment of the cells with the CCK2 receptor specific antagonist, L365,260, inhibited gastrin-induced COX-2 protein and mRNA expression. Pretreatment with L364,714, the CCK1 receptor specific antagonist did not block COX-2 induction by gastrin. Inhibition of de novo protein synthesis by cycloheximide did not block COX-2 mRNA induction by gastrin. Also, gastrin-dependent COX-2 expression did not require PKC activity, activation of ERK, or transactivation of EGFR. However, co-stimulation with EGF and gastrin synergistically induced COX-2 protein and mRNA expression and PGE2 secretion. Measurements of COX-2 mRNA stability and COX-2 gene transcription reveal that EGF significantly increased the half-life of COX-2 mRNA with only a slight increase in the COX-2 transcription rate. Conversely, gastrin significantly increased COX-2 gene transcription rates but did not enhance COX-2 mRNA stability.
Slice
Lee W
LW
Division of Digestive Diseases, Department of Medicine, CURE: Digestive Diseases Research Center, Greater Los Angeles VA Medical Center, University of California, Los Angeles, California, USA. lslice@mednet.ucla.edu
Hodikian
Raffi
R
Zhukova
Elena
E
D016475:3T3 Cells; D000818:Animals; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000378:metabolism; D004357:Drug Synergism; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000378:metabolism; D005347:Fibroblasts; D005755:Gastrins / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D043887:Receptor, Cholecystokinin B; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface / Q000378:metabolism; D011949:Receptors, Cholecystokinin / Q000378:metabolism*; D014158:Transcription, Genetic
D005755:Gastrins; D007527:Isoenzymes; D012333:RNA, Messenger; D043887:Receptor, Cholecystokinin B; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; D011949:Receptors, Cholecystokinin; D004815:Epidermal Growth Factor; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D066246:ErbB Receptors; D020928:Mitogen-Activated Protein Kinases; D015232:Dinoprostone