EXPRESSION OF BETA-CATENIN AND GAMMA-CATENIN IN EPITHELIAL TUMOR-CELLLINES AND CHARACTERIZATION OF A UNIQUE CELL-LINE

In addition to its structural role, beta-catenin has recently been ide ntified as an oncogene, while its homologue gamma-catenin (plakoglobin ) seems to suppress tumorigenicity. Twenty-five epithelial tumor cell lines were screened; 18 expressed both beta- and gamma-catenin, two ex pressed neither protein, four showed beta- but not gamma-catenin expre ssion, while only one cell line showed gamma- but not beta-catenin exp ression. As per literature search, the cell line expressing gamma- but not beta-catenin appeared to be unique. This cell line, SKBR-3, is a human breast cancer cell line which does not express beta-catenin or E -cadherin protein. There is, however, expression of beta-catenin, but not E-cadherin, mRNA. In order to determine the mechanism for this uni que expression pattern, SKBR-3 cells were transfected with E-cadherin which resulted in expression of beta-catenin protein, Immunofluorescen t staining of the E-cadherin transfected SKBR-3 cells revealed beta-ca tenin in the adherens junctions while transfection with just an epitop e tagged (VSV) beta-catenin showed expression only in the nucleus. Dou ble transfection with E-cadherin and VSV beta-catenin showed the beta- catenin in the adherens junction of the E-cadherin transfected cells. These results indicate that the mechanism for the lack of beta-catenin expression in the SKBR-3 cell line is possibly post-translational deg radation and that when E-cadherin is transfected into these cells, the beta-catenin is stabilized in the adherens junction and not degraded. This cell line should be of interest to those studying the role of th e homologues, beta- and gamma-catenin, in cancer pathogenesis. Publish ed by Elsevier Science Ireland Ltd.