Characterization of a tumor cell surface protein with heterologous antisera to a spontaneous BALB/c lung carcinoma

Abstract

Line 1, a spontaneous alveolar carcinoma from a BALB/c mouse, is highly metastatic and weakly antigenic in the syngeneic host. Sera and enriched antibody preparations were made specific for line 1 cells by in vitro and in vivo absorptions. By lactoperoxidase-catalyzed radioiodination of cell surface protein followed by precipitation with specific antibodies, a protein with a molecular weight of about 180,000 (designated TSP-180) was identified that was present on line 1 cells but not on normal lung cells or Moloney sarcoma tumor cells. Studies of competition for immune precipitation of TSP-180 by unlabeled protein preparations from various sources indicate that (a) TSP-180 is present in tumor cells of various culture passage levels, (b) tumor cells grown i.m. also contain TSP-180, and (c) normal lung proteins compete weakly, and only at very high protein concentrations. A protein similar to TSP-180 was detected on Madison 109 carcinoma and on three other lung carcinomas adapted to culture. Experiments with specific antisera show that TSP-180 is not lactoperoxidase, fetal bovine serum protein, large external transformation-sensitive protein, or an antigen related to murine leukemia virus proteins.