Regulation of the tumor suppressor FOXO3 by the thromboxane-A2 receptors in urothelial cancer

PLoS One. 2014 Sep 9;9(9):e107530. doi: 10.1371/journal.pone.0107530. eCollection 2014.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / pharmacology
  • Butadienes / pharmacology
  • Cell Line
  • Cell Line, Tumor
  • Cell Movement / drug effects
  • Cell Movement / genetics
  • Cytoplasm / drug effects
  • Cytoplasm / genetics
  • Forkhead Box Protein O3
  • Forkhead Transcription Factors / genetics*
  • Humans
  • MAP Kinase Signaling System / drug effects
  • MAP Kinase Signaling System / genetics
  • Nitriles / pharmacology
  • Phosphorylation / drug effects
  • Phosphorylation / genetics
  • Receptors, Thromboxane A2, Prostaglandin H2 / genetics*
  • Signal Transduction / drug effects
  • Signal Transduction / genetics
  • Sirtuin 1 / genetics
  • Superoxide Dismutase / genetics
  • Transcription, Genetic / drug effects
  • Transcription, Genetic / genetics
  • Tumor Suppressor Proteins / genetics*
  • Urologic Neoplasms / genetics*

Substances

  • Butadienes
  • FOXO3 protein, human
  • Forkhead Box Protein O3
  • Forkhead Transcription Factors
  • Nitriles
  • Receptors, Thromboxane A2, Prostaglandin H2
  • Tumor Suppressor Proteins
  • U 0126
  • 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid
  • Superoxide Dismutase
  • SIRT1 protein, human
  • Sirtuin 1