Regulation of constitutive cyclooxygenase-2 expression in colon carcinoma cells.
Cyclooxygenase-2 (COX-2) is not normally expressed in the human large intestine, but its levels are increased in the majority of human colorectal carcinomas. Here we investigate the regulation of constitutive COX-2 expression and prostaglandin production in human colorectal carcinoma cells. Both COX-2 mRNA and protein were expressed in well differentiated HCA-7, Moser, LS-174, and HT-29 cells, albeit at different levels. COX-2 expression was not detected in several poorly differentiated colon cancer cell lines including DLD-1. Transcriptional regulation played a key role for the expression of COX-2 in human colon carcinoma cells, and both the nuclear factor for interleukin-6 regulatory element and the cAMP-response element were responsible for regulation of COX-2 transcription. COX-2 mRNA was more stable in HCA-7 cells than in the other cell lines tested. Both transcriptional and post-transcriptional regulation of COX-2 involved the MAP kinase pathway. Modulation of the Akt/protein kinase B or Rho B signaling pathways altered the levels of COX-2 expression. Furthermore, COX-2 protein is degraded through ubiquitin proteolysis, and its half-life was approximately 3.5-8 h. HCA-7 cells produced significant quantities of prostaglandin E(2) and other prostaglandins. Moser and LS-174 cells also generated prostaglandins, but levels were significantly lower than that observed in HCA-7 cells.
Shao
J
J
Departments of Medicine, Pharmacology, and Cell Biology, Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Department of Veterans Affairs Medical Center, Nashville, Tennessee 37232, USA.
Sheng
H
H
Inoue
H
H
Morrow
J D
JD
DuBois
R N
RN
D003110:Colonic Neoplasms / Q000201:enzymology*; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000096:biosynthesis; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins; D011401:Promoter Regions, Genetic; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D020743:rhoB GTP-Binding Protein / Q000502:physiology
D007527:Isoenzymes; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020743:rhoB GTP-Binding Protein; D015232:Dinoprostone