Monoclonal antibody L/1C2 reactive with a human carcinoma associated antigen

A murine IgG3 monoclonal antibody which defines a human carcinoma associated antigen is described. The antibody, designated L/1C2, was made against a human lung squamous cell carcinoma line designated USCLS-1. It reacts with the surface of 15 of 16 viable human carcinoma cell lines and was detected in 70 of 78 frozen sections of human carcinomas. Melanoma cell lines and frozen sections of melanomas and a lymphoma were unreactive. Normal tissue reactivity included vessels, plus some ducts, glandular structures, and epithelial surfaces. Similar normal tissue reactivity patterns were seen with Rhesus monkey tissue samples. Immunoprecipitation studies indicate that L/1C2 reacts with a glycoprotein doublet which migrates in the range of 110,000 to 140,000 Mr under reducing conditions. Fluorescence analysis suggests this antigen is internalized following reaction with the L/1C2 antibody. Using in vitro human tumor cell growth inhibition assays, it was possible to achieve significant growth inhibition with L/1C2, while another target cell-reactive antibody in the same assay had no inhibitory effect.