title: Expression of the tumor suppressor protein 14-3-3 sigma is down-regulated in invasive transitional cell carcinomas of the urinary bladder undergoing epithelial-to-mesenchymal transition.
abstract: The 14-3-3 proteins constitute a family of abundant, highly conserved and broadly expressed acidic polypeptides that are involved in the regulation of various cellular processes such as cell-cycle progression, cell growth, differentiation, and apoptosis. One member of this family, the 14-3-3 isoform sigma, is expressed only in epithelial cells and is frequently down-regulated in a variety of human cancers. To determine the prevalence of 14-3-3 sigma silencing in bladder cancer progression, we have studied the expression of this protein in normal urothelium and bladder transitional cell carcinomas (TCCs) of various grades and stages using two-dimensional gel electrophoresis in combination with Western blotting and immunohistochemistry. We show that the expression of 14-3-3 sigma is down-regulated in invasive TCCs, particularly in lesions that are undergoing epithelial-to-mesenchymal conversion. Altered expression of 14-3-3 sigma in invasive TCCs is not due to increased externalization of the protein nor to an aberrant proliferative potential of neoplastic cells. Furthermore, we found that impaired 14-3-3 sigma expression is not associated with increased levels of the dominant-negative transcriptional regulator Delta Np63. Down-regulation of 14-3-3 sigma was confirmed by indirect immunofluorescence using a peptide-based rabbit polyclonal antibody specific for this protein. We also show that the expression of 14-3-3 sigma is highly up-regulated in pure squamous cell carcinomas. Taken together, these results provide evidence that deregulation of 14-3-3 sigma may play a key role in bladder cancer progression, in particular in differentiation events leading to epithelial-to-mesenchymal transition and stratified squamous metaplasia.
authors.affiliation: Institute of Cancer Biology, Danish Cancer Society, Copenhagen, Denmark. jom@cancer.dk
authors.forename: José M A
authors.initials: JM
authors.lastname: Moreira
authors.forename: Pavel
authors.initials: P
authors.lastname: Gromov
authors.forename: Julio E
authors.initials: JE
authors.lastname: Celis
mesh_terms: D048948:14-3-3 Proteins; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000473:pathology; D002295:Carcinoma, Transitional Cell / Q000378:metabolism* / Q000473:pathology; D002454:Cell Differentiation; D002455:Cell Division; D002478:Cells, Cultured; D015536:Down-Regulation; D015180:Electrophoresis, Gel, Two-Dimensional; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D020868:Gene Silencing; D005799:Genes, Dominant; D016147:Genes, Tumor Suppressor; D006801:Humans; D007124:Immunoenzyme Techniques; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism; D009361:Neoplasm Invasiveness / Q000473:pathology; D040901:Proteomics / Q000379:methods*; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*; D001743:Urinary Bladder / Q000378:metabolism / Q000473:pathology; D001749:Urinary Bladder Neoplasms / Q000378:metabolism* / Q000473:pathology; D014551:Urinary Tract / Q000473:pathology
chemical_list: D048948:14-3-3 Proteins; D014446:Tyrosine 3-Monooxygenase