Expression of the Tumor Suppressor Protein 14-3-3σ Is Down-regulated in Invasive Transitional Cell Carcinomas of the Urinary Bladder Undergoing Epithelial-to-Mesenchymal Transition

José M. A. Moreira, Pavel Gromov, Julio E. Celis
2004 Molecular & Cellular Proteomics  
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 , 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 silencing in bladder cancer progression, we have studied
more » ... on, 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 is downregulated in invasive TCCs, particularly in lesions that are undergoing epithelial-to-mesenchymal conversion. Altered expression of 14-3-3 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 expression is not associated with increased levels of the dominant-negative transcriptional regulator ⌬Np63. Down-regulation of 14-3-3 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 is highly up-regulated in pure squamous cell carcinomas. Taken together, these results provide evidence that deregulation of 14-3-3 may play a key role in bladder cancer progression, in particular in differentiation events leading to epithelial-to-mesenchymal transition and stratified squamous metaplasia.
doi:10.1074/mcp.m300134-mcp200 pmid:14736829 fatcat:ghamyh2dozecblcpda636ud2ue