RESUMO
PURPOSE: Cadherins are cell surface glycoproteins that mediate Ca2+-dependent, homophilic cell-cell adhesion. The classical cadherins, E-, P- and N-cadherins, are known to self-associate from their extracellular domain, while their cytoplasmic domain interacts with either beta-catenin or plakoglobin (gamma-catenin), which in turn is bound to alpha-catenin that links the complex to the actin cytoskeleton. The aim of the present study was to analyze the expression of E-, P- and N-cadherins and catenins in human bladder carcinoma cells. MATERIALS AND METHODS: Five human bladder carcinoma cell lines, representing a variety of differentiation states, were grown in cell culture. We performed a cell aggregation assay, specific for biological cadherin activity. The expression of cadherins and catenins was analyzed by immunocytochemistry, Western blotting and RT-PCR. The interactions between cadherins and catenins were assessed by immunoprecipitation. RESULTS: We observed a reduced E-cadherin expression in the poorly differentiated and invasive-tumor derived cells. Interestingly, immunofluorescence study reveals the persistent localization of catenins at intercellular contacts in two E-cadherin deficient cell lines (T24 and TCCSUP) which yet exhibit an epithelial-like morphology and a calcium-dependent adhesive capacity. This suggests that other cadherin(s) are expressed in these both cell lines. P-cadherin, another epithelial cadherin, is expressed only in E-cadherin positive cells. On the other hand, N-cadherin is present at cell-cell borders in the very anaplastic cell lines, T24 and TCCSUP, and is able to link beta-catenin or plakoglobin. CONCLUSION: These results indicate that N-cadherin may participate in intercellular adhesion, while facilitating bladder tumorigenesis.
