Induction of cyclooxygenase-2 by activated Ha-ras oncogene in Rat-1 fibroblasts and the role of mitogen-activated protein kinase pathway.
Elevated cyclooxygenase-2 (COX-2) expression and activity have been observed in several different transformed cell types that express mutated ras genes. To investigate the mechanism of increased COX-2 expression following Ras-mediated transformation, Rat-1:iRas cell line was transfected with an Ha-RasVal-12 cDNA expression vector that is under the transcriptional control of the lac operon and is inducible with isopropyl-1-thio-beta-D-galactopyranoside (IPTG). IPTG treatment caused parallel increases in the levels of Ha-Ras and COX-2 proteins in Rat-1:iRas cells. The increased expression of COX-2 was accompanied by increased prostaglandin E2 production. Selective inhibition of COX-2 activity suppressed the production of prostaglandin E2 by >90% but did not alter the progress of the morphological transformation. The level of COX-2 mRNA was up-regulated by activated Ha-Ras. Induction of Ras increased the transcription of COX-2 by 44.3 +/- 10.1% and increased the half-life of COX-2 mRNA by approximately 3.5-fold. A specific mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) inhibitor (PD 98059) caused a delay in both the activation of ERK1/2 and the induction of COX-2 in IPTG-induced Rat-1:iRas cells. Inhibition of ERK activity by PD 98059 also suppressed the induction of COX-2 by epidermal growth factor in intestinal epithelial cells and significantly reduced the expression of COX-2 in Ha-Ras-transformed rat intestinal epithelial cells. ERK activity appears to be required for induction of COX-2 by Ras.
Sheng
H
H
Department of Surgery,the Vanderbilt Cancer Center, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
Williams
C S
CS
Shao
J
J
Liang
P
P
DuBois
R N
RN
Beauchamp
R D
RD
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D004790:Enzyme Induction; D066246:ErbB Receptors / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D011905:Genes, ras; D007527:Isoenzymes / Q000096:biosynthesis*; D007544:Isopropyl Thiogalactoside / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D051381:Rats
D007527:Isoenzymes; D007544:Isopropyl Thiogalactoside; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D066246:ErbB Receptors; D017871:Calcium-Calmodulin-Dependent Protein Kinases