title: Microsomal prostaglandin E2 synthase-1 is induced by conditional expression of RET/PTC in thyroid PCCL3 cells through the activation of the MEK-ERK pathway.
abstract: RET/PTC rearrangements are believed to be tumor-initiating events in papillary thyroid carcinomas. We identified microsomal prostaglandin E2 synthase-1 (mPGES-1) as a RET/PTC-inducible gene through subtraction hybridization cloning and expression profiling with custom microarrays. The inducible prostaglandin E2 (PGE2) biosynthetic enzymes cyclooxygenase-2 (COX-2) and mPGES-1 are up-regulated in many cancers. COX-2 is overexpressed in thyroid malignancies compared with benign nodules and normal thyroid tissues. Eicosanoids may promote tumorigenesis through effects on tumor cell growth, immune surveillance, and angiogenesis. Conditional RET/PTC1 or RET/PTC3 expression in PCCL3 thyroid cells markedly induced mPGES-1 and COX-2. PGE2 was the principal prostanoid and up-regulated (by approximately 60-fold), whereas hydroxyeicosatetraenoic acid metabolites were decreased, consistent with shunting of prostanoid biosynthesis toward PGE2 by coactivation of the two enzymes. RET/PTC activated mPGES-1 gene transcription. Based on experiments with kinase inhibitors, with PCCL3 cell lines with doxycycline-inducible expression of RET/PTC mutants with substitutions of critical tyrosine residues in the kinase domain, and lines with inducible expression of activated mutants of H-RAS and MEK1, RET/PTC was found to regulate mPGES-1 through Shc-RAS-MEK-ERK. These data show a direct relationship between activation of a tyrosine kinase receptor oncogene and regulation of PGE2 biosynthesis. As enzymes involved in prostanoid biosynthesis can be targeted with pharmacological inhibitors, these findings may have therapeutic implications.
authors.affiliation: Division of Endocrinology and Metabolism, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267, USA.
authors.forename: Efisio
authors.initials: E
authors.lastname: Puxeddu
authors.forename: Norisato
authors.initials: N
authors.lastname: Mitsutake
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Knauf
authors.forename: Sonia
authors.initials: S
authors.lastname: Moretti
authors.forename: Hei W
authors.initials: HW
authors.lastname: Kim
authors.forename: Karen A
authors.initials: KA
authors.lastname: Seta
authors.forename: Diane
authors.initials: D
authors.lastname: Brockman
authors.forename: Leslie
authors.initials: L
authors.lastname: Myatt
authors.forename: David E
authors.initials: DE
authors.lastname: Millhorn
authors.forename: James A
authors.initials: JA
authors.lastname: Fagin
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D002291:Carcinoma, Papillary / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D017077:Culture Media, Conditioned / Q000494:pharmacology; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000378:metabolism; D018450:Disease Progression; D004305:Dose-Response Relationship, Drug; D015777:Eicosanoids / Q000378:metabolism; D015723:Gene Library; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000378:metabolism; D019746:Intramolecular Oxidoreductases / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D008565:Membrane Proteins; D009154:Mutation; D009693:Nucleic Acid Hybridization; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D000071876:Prostaglandin-E Synthases; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000235:genetics; D051096:Proto-Oncogene Proteins c-ret; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014443:Tyrosine / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D017077:Culture Media, Conditioned; D015777:Eicosanoids; D006893:Hydroxyeicosatetraenoic Acids; D007527:Isoenzymes; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D014443:Tyrosine; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases; C495001:Ret protein, rat; D019746:Intramolecular Oxidoreductases; C000605862:PTGES protein, human; D000071876:Prostaglandin-E Synthases; D015232:Dinoprostone