title: The cyclooxygenase inhibitor sulindac sulfide inhibits EP4 expression and suppresses the growth of glioblastoma cells.
abstract: EP4 expression in human glioblastoma cells correlates with growth on soft agar. The cyclooxygenase inhibitor sulindac sulfide first altered specificity protein-1 (Sp-1) and early growth response gene-1 expression, then increased the expression of nonsteroidal anti-inflammatory drug-activated gene 1 and activating transcription factor 3, and then decreased EP4 expression. EP4 suppression was dependent on blocking the Sp-1 binding sites in the human EP4 promoter. Mutation in the Sp-1 sites in EP4 altered the promoter activity and abolished sulindac sulfide effects. The inhibitory effect of sulindac sulfide on EP4 expression was reversed by PD98059, a mitogen-activated protein/extracellular signal-regulated kinase kinase-1/extracellular signal-regulated kinase inhibitor. Sp-1 phosphorylation was dependent on sulindac sulfide-induced Erk activation. Chromatin immunoprecipitation assay confirmed that Sp-1 phosphorylation decreases Sp-1 binding to DNA and leads to the suppression of EP4. Inhibition of cell growth on soft agar assay was found to be a highly complex process and seems to require not only the inhibition of cyclooxygenase activity but also increased expression of nonsteroidal anti-inflammatory drug-activated gene 1 and activating transcription factor 3 and suppression of EP4 expression. Our data suggest that the suppression of EP4 expression by sulindac sulfide represents a new mechanism for understanding the tumor suppressor activity.
authors.affiliation: Laboratory of Molecular Carcinogenesis, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709, USA.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kambe
authors.forename: Hiroki
authors.initials: H
authors.lastname: Yoshioka
authors.forename: Hideki
authors.initials: H
authors.lastname: Kamitani
authors.forename: Takashi
authors.initials: T
authors.lastname: Watanabe
authors.forename: Seung Joon
authors.initials: SJ
authors.lastname: Baek
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Eling
mesh_terms: D051700:Activating Transcription Factor 3 / Q000378:metabolism; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000473:pathology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D047369:Chromatin Immunoprecipitation; D003114:Colony-Forming Units Assay; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D051766:Early Growth Response Protein 1 / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D005909:Glioblastoma / Q000473:pathology*; D006801:Humans; D047468:Immunoprecipitation; D008156:Luciferases / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D018078:Receptors, Prostaglandin E / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D058309:Receptors, Prostaglandin E, EP4 Subtype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016329:Sp1 Transcription Factor / Q000378:metabolism; D013467:Sulindac / Q000031:analogs & derivatives* / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D051700:Activating Transcription Factor 3; D000894:Anti-Inflammatory Agents, Non-Steroidal; D016861:Cyclooxygenase Inhibitors; D051766:Early Growth Response Protein 1; D005419:Flavonoids; C117339:NBAS protein, human; D009363:Neoplasm Proteins; C545650:PTGER4 protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018078:Receptors, Prostaglandin E; D058309:Receptors, Prostaglandin E, EP4 Subtype; D016329:Sp1 Transcription Factor; D013467:Sulindac; C025462:sulindac sulfide; D008156:Luciferases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one