Monoclonal antibodies directed against rat tracheal epithelial cells transformed in vitro

Cloned hybridoma cell lines were obtained by fusion of murine myeloma cells with spleen lymphocytes of either F344 rats or BALB/c mice immunized against the malignant F344 tracheal cell line, 2-10-1. Monoclonal antibodies were selected for their ability to bind to the immunizing cell line and not to normal tracheal epithelial cells. Results from quantitative binding assays indicated that such monoclonal antibodies recognized six epitopes. Each epitope was detected on four other malignant tracheal epithelial cell lines, and was also expressed during early preneoplastic cell passages (i.e. before the cells acquired the ability to produce carcinomas in vivo). Quantitative differences in epitope expression between non-tumorigenic and tumorigenic passages of individual cell lines could not be detected for five of the epitope groups. However, two monoclonal antibodies, recognizing the same epitope, did show quantitative binding differences between non-tumorigenic and tumorigenic cell passages on three of the five cell lines tested. Our results show that carcinogen-altered tracheal cell populations can be distinguished from non-altered cells (by our current assay methods) by use of monoclonal antibodies. The suggest that the antigen expression is an early event associated with the transformation of rat tracheal epithelial cells in culture.