title: Lack of cyclooxygenase-2 activity in HT-29 human colorectal carcinoma cells.
abstract: Induction of cyclooxygenase-2 (COX-2) is an early event in the sequence of polyp formation to colon carcinogenesis. COX-2 is at elevated levels in human colorectal cancers and in tumors and polyps of mouse models of colorectal cancer. Mutation of the adenomatous polyposis coli (APC) gene is the initial event leading to colorectal cancer. Colorectal cells in culture which express mutant APC are often used to examine the association of COX-2 expression and apoptosis. The expression of full-length APC in HT-29 cells, a human colorectal carcinoma cell line which normally expresses truncated APC and highly expresses COX-2, inhibits cell growth through increased apoptosis and results in a down-regulation of COX-2 protein. In this report, we examine whether down-regulation of COX-2 is directly linked to the increase in apoptosis observed in these HT-29-APC cells. We present evidence that COX-2 and apoptosis are not linked since COX-2, although expressed, is catalytically inactive. Interestingly, the COX-2 cloned from HT-29 cells is catalytically active when transfected into HCT-116 cells, a colorectal cell line which normally does not express COX-2, but is not active in the HT-29 cell line itself.
authors.affiliation: Eicosanoid Biochemistry Section, Laboratory of Molecular Carcinogenesis, Research Triangle Park, North Carolina 27709, USA.
authors.forename: L C
authors.initials: LC
authors.lastname: Hsi
authors.forename: S J
authors.initials: SJ
authors.lastname: Baek
authors.forename: T E
authors.initials: TE
authors.lastname: Eling
mesh_terms: D017209:Apoptosis; D015153:Blotting, Western; D002851:Chromatography, High Pressure Liquid; D015179:Colorectal Neoplasms; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015536:Down-Regulation; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology*; D008565:Membrane Proteins; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism* / Q000494:pharmacology*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D008565:Membrane Proteins; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D007213:Indomethacin