LOCALIZATION OF A M, 52,000 KERATIN IN BASAL EPITHELIAL-CELLS OF THE MOUSE BLADDER AND EXPRESSION THROUGHOUT NEOPLASTIC PROGRESSION

Abstract

The isolation of a 52,000 MW keratin from a nontumorigenic bladder epithelial cell line and its localization, by immunofluorescence, in bladder frozen sections at diffrent stages of neoplastic progression and in various carcinogen-transformed bladder epithelial cells and human bladder carcinoma-derived cell lines are reported. The 52,000 MW keratin was present in basal epithelial cells of the normal bladder but absent from the intermediate and superficial epithelical cell layers. Hyperplastic bladder lesions induced in mice after the administration of butyl-(4-hydroxybutyl)-nitrosamine resulted primarily from the proliferation of cells in the basal compartment. Butyl-(4-hydroxybutyl)nitrosamine-induced bladder carcinomas displayed differential staining with the anti-52,000 MW keratin antiserum, reflecting divergent differentiated status within a tumor and a subpopulation of cells with reduced overall keratin expression. Primary cultures of bladder carcinomas revealed a subpopulation of cells with limited filamentous keratin as was observed in vivo. Mouse bladder epithelial cell lines transformed in culture by a chemical carcinogen showed a loss or reduction in expression of the 52,000 MW keratin. Two human bladder carcinoma cell lines displayed very limited expression of the 52,000 MW keratin. Although the loss or reduction in expression of a specific keratin in unlikely to be responsible for transformation, it may contribute to the heterogeneity in the differentiated state and morphology of bladder epithelial cells during neoplastic progression both in vivo and in culture.