Control of COX-2 gene expression through peroxisome proliferator-activated receptor gamma in human cervical cancer cells.

Abstract

PURPOSE:

The peroxisome proliferator-activated receptor-gamma (PPARgamma), a ligand-dependent transcription factor belonging to the family of nuclear receptors, has been implicated in the control of cyclooxygenase (COX) 2 expression in some tissue, although the exact mechanism(s) of this activity has not been elucidated. In this study we explored the possible mechanism(s) of control of COX-2 gene expression through PPARgamma signaling in human cervical cancer.

EXPERIMENTAL DESIGN:

Using primary human cervical tissues and the CaSki human cervical cancer cell line, we assayed for PPARgamma and COX-2 mRNA expression by reverse transcription-PCR. Nuclear protein binding activities to three response elements located in the COX-2 promoter [nuclear factor kappaB (NFkappaB), cyclic AMP response element, and activator protein (AP)-2] were measured by gel mobility shift assays. We used transient transfection assays with COX-2 promoter reporter gene constructs to determine the regulatory sites in this promoter, which mediates PPARgamma regulation of COX-2 activity.

RESULTS:

We showed, for the first time, that primary human cervical cancer tissues express PPARgamma. Using CaSki cells, we demonstrated that COX-2 and PPARgamma mRNA levels were inversely regulated by PPARgamma ligands in that these compounds up-regulated PPARgamma but down-regulated COX-2. In contrast, epidermal growth factor (EGF), a potent activator of COX-2, decreased PPARgamma mRNA levels. This down-regulation of PPARgamma mRNA by EGF was blocked in the presence of NS-398, a selective COX-2 inhibitor. PPARgamma ligands suppressed the binding activities of AP-1 (binding to CRE) and NFkappaB but not AP-2. Transient transfection results indicated that EGF stimulated whereas PPARgamma ligands inhibited COX-2 promoter (-327/+59) activity. This effect by PPARgamma ligands on the COX-2 promoter was blocked when the CRE, but not the NFkappaB, binding site was mutagenized.

CONCLUSION:

Cervical cancer cells express readily detectable levels of PPARgamma. There is reciprocal negative regulation between COX-2 and PPARgamma signaling in human cervical cancer cells. The ability of PPARgamma ligands to inhibit COX-2 appears to be mediated predominantly through inhibition of AP-1 protein binding to the CRE site in the COX-2 promoter.

• Authors: Shouwei Han, Hiroyasu Inoue, Lisa C Flowers, Neil Sidell
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 9 Issue 12 Pg. 4627-35 (Oct 01 2003) ISSN: 1078-0432 [Print] United States
• PMID: 14555539 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Cyclic AMP Response Element-Binding Protein
• Cyclooxygenase 2 Inhibitors
• Cyclooxygenase Inhibitors
• DNA-Binding Proteins
• Isoenzymes
• Membrane Proteins
• NF-kappa B
• Nitrobenzenes
• RNA, Messenger
• Receptors, Cytoplasmic and Nuclear
• Sulfonamides
• Transcription Factor AP-1
• Transcription Factor AP-2
• Transcription Factors
• N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide
• Epidermal Growth Factor
• Cyclooxygenase 2
• PTGS2 protein, human
• Prostaglandin-Endoperoxide Synthases

Topics

• Cyclic AMP Response Element-Binding Protein (genetics, metabolism)
• Cyclooxygenase 2
• Cyclooxygenase 2 Inhibitors
• Cyclooxygenase Inhibitors (pharmacology)
• DNA-Binding Proteins (genetics, metabolism)
• Electrophoretic Mobility Shift Assay
• Epidermal Growth Factor (pharmacology)
• Female
• Gene Expression Regulation, Enzymologic
• Humans
• Isoenzymes (antagonists & inhibitors, genetics, metabolism)
• Membrane Proteins
• NF-kappa B (genetics, metabolism)
• Nitrobenzenes (pharmacology)
• Promoter Regions, Genetic (genetics)
• Prostaglandin-Endoperoxide Synthases (genetics, metabolism)
• RNA, Messenger (genetics, metabolism)
• Receptors, Cytoplasmic and Nuclear (antagonists & inhibitors, genetics, metabolism)
• Response Elements
• Sulfonamides (pharmacology)
• Transcription Factor AP-1 (metabolism)
• Transcription Factor AP-2
• Transcription Factors (antagonists & inhibitors, genetics, metabolism)
• Transcriptional Activation
• Transfection
• Tumor Cells, Cultured
• Uterine Cervical Neoplasms (genetics, metabolism)