Differential regulation of cyclooxygenase-2 in nontransformed and ras-transformed intestinal epithelial cells.
To determine signaling pathways responsible for modulation of COX-2 expression in nontransformed and transformed epithelial cells, we studied a rat intestinal epithelial (RIE) cell line expressing constitutively active Ras and RhoA. Expression of COX-2 protein was higher in RIE-RhoA(63L) (four-fold) and RIE-Ras(12V) (seven-fold) cells than in parental cells. Prior work suggests that Ras hyperactivity induces the expression of transforming growth factor (TGF)beta and increases epidermal growth factor (EGF)-related peptide signaling-possible mechanisms for increased COX-2 expression. Expression of COX-2 was stimulated by TGFbeta and TGFalpha in RIE and RIE-Rho(63L) cells, but not further stimulated in RIE-Ras(12V) cells. PD153035, an inhibitor of EGF receptor tyrosine kinase, and PD98059, an inhibitor of Erk, attenuated COX-2 expression in RIE and RIE-RhoA(63L). However, the high levels of COX-2 expression in RIE-Ras(12V) cells were not inhibited by either compound. Titration with a pan-neutralizing anti-TGFbeta antibody did not decrease COX-2 in RIE-Ras(12V) cells, even with concurrent EGFR inhibition. Thus, stimulation of the EGF receptor is important in the modulation of COX-2 expression in nontransformed RIE and RIE-RhoA(63L) cells. In Ras-transformed cells, signaling by additional Ras effector pathways, perhaps the RhoA pathway, must be invoked. Identification of these pathways is critical for therapeutic manipulation of COX-2 expression.
Du
Jianguo
J
Department of Pediatrics, Center for Cell and Vascular Biology, Columbus Children's Research Institute, Columbus, OH 43205, USA.
Jiang
Bo
B
Barnard
John
J
D000818:Animals; D002460:Cell Line; D002461:Cell Line, Transformed; D049109:Cell Proliferation; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D015232:Dinoprostone / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D007413:Intestinal Mucosa / Q000187:drug effects / Q000201:enzymology; D051381:Rats; D016211:Transforming Growth Factor alpha / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D018631:ras Proteins / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D016211:Transforming Growth Factor alpha; D016212:Transforming Growth Factor beta; D051546:Cyclooxygenase 2; D066246:ErbB Receptors; D018631:ras Proteins; D020742:rhoA GTP-Binding Protein; D015232:Dinoprostone