title: Regulation of the tumor suppressor FOXO3 by the thromboxane-A2 receptors in urothelial cancer.
abstract: The transcription factor FOXO3 is a well-established tumor suppressor whose activity, stability, and localization are regulated by phosphorylation and acetylation. Previous data by our laboratory demonstrated amplified thromboxane-A2 signaling was associated with poor prognoses in bladder cancer patients and overexpression of the thromboxane-A2 isoform-β receptor (TPβ), but not TPα, induced malignant transformation of immortalized bladder cells in vivo. Here, we describe a mechanism of TP mediated modulation of FOXO3 activity and localization by phosphorylation and deacetylation in a bladder cancer cell model. In vitro gain and loss of function studies performed in non-transformed cell lines, UROsta and SV-HUC, revealed knockdown of FOXO3 expression by shRNA increased cell migration and invasion, while exogenously overexpressing TPβ raised basal phosphorylated (p)FOXO3-S294 levels. Conversely, overexpression of ERK-resistant, mutant FOXO3 reduced increases in UMUC3 cell migration and invasion, including that mediated by TP agonist (U46619). Additionally, stimulation of UMUC3 cells with U46619 increased pFOXO3-S294 expression, which could be attenuated by treatment with a TP antagonist (PTXA2) or ERK inhibitor (U0126). Initially U46619 caused nuclear accumulation of pFOXO3-S294; however, prolonged stimulation increased FOXO3 cytoplasmic localization. U46619 stimulation decreased overall FOXO3 transcriptional activity, but was associated with increased expression of its pro-survival target, manganese superoxide dismutase. The data also shows that TP stimulation increased the expression of the histone deacetylase, SIRT1, and corresponded with decreased acetylated-FOXO3. Collectively, the data suggest a role for TP signaling in the regulation of FOXO3 activity, mediated in part through phosphorylation and deacetylation.
authors.affiliation: Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, South Carolina, United States of America; Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, United States of America.
authors.forename: Philip M
authors.initials: PM
authors.lastname: Sobolesky
authors.affiliation: Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, United States of America; Departments of Pharmacology and Medicine, Medical University of South Carolina, Charleston, South Carolina, United States of America.
authors.forename: Perry V
authors.initials: PV
authors.lastname: Halushka
authors.affiliation: Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, United States of America; Department of Public Health Sciences, Medical University of South Carolina, Charleston, South Carolina, United States of America.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Garrett-Mayer
authors.affiliation: Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, South Carolina, United States of America.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Smith
authors.affiliation: Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, South Carolina, United States of America; Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, United States of America.
authors.forename: Omar
authors.initials: O
authors.lastname: Moussa
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D002070:Butadienes / Q000494:pharmacology; D002460:Cell Line; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000235:genetics; D003593:Cytoplasm / Q000187:drug effects / Q000235:genetics; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000235:genetics; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000235:genetics*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D056564:Sirtuin 1 / Q000235:genetics; D013482:Superoxide Dismutase / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000235:genetics*; D014571:Urologic Neoplasms / Q000235:genetics*
chemical_list: D002070:Butadienes; C499517:FOXO3 protein, human; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D009570:Nitriles; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D025521:Tumor Suppressor Proteins; C113580:U 0126; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D013482:Superoxide Dismutase; C447939:SIRT1 protein, human; D056564:Sirtuin 1