Analysis of surface proteins of mouse lung carcinomas using monoclonal antibodies

Hybridoma cultures secreting monoclonal antibodies were derived from fusions of parent myeloma P3-X63-Ag8 with spleen cells of F344 rats which had been immunized with the BALB/c alveolar lung carcinoma line 1. Screening of several thousand hybridoma cultures identified 55 cell lines making antibody that bound to the line 1 cell surface. Of 15 of these antibodies tested, seven could be identified as binding to P100, a surface protein expressed on both normal and tumor cells, and five reacted with a tumor surface protein with a molecular weight of 180,000 (TSP-180) not found on control cell lines. Monoclonal antibodies to TSP-180 bound to lung tumor cells but not to normal cells or tumors of other organs. Five different hybridoma cultures secreting antibody to TSP-180 were cloned, and monoclonal antibodies were purified by affinity chromatography. Radioiodinated monoclonal antibodies were used to determine affinity constants for binding to TSP-180 as it is expressed on four different mouse lung tumors. Binding constants ranged from 1.2 X 10(7) to 1.5 X 10(8) liters/mol for the different antibodies.