Monoclonal antibody 44-3A6 as a probe for a novel antigen found on human lung carcinomas with glandular differentiation.

This paper describes an immunoglobulin G1 mouse monoclonal antibody (MCA) 44-3A6 directed against a human adenocarcinoma of the lung, cell line A549. This hybrid is a fusion product of the mouse myeloma SP 2/0.Ag14 and spleen cells from a BALB/c mouse which had been hyperimmunized with A549. Live cell radioimmunoassays, immunofluorescences, and fluorescent activated cell sorter analysis indicate that MCA 44-3A6 reacts with a cell surface antigen. Western blot analysis identifies a major antigen band with the apparent molecular weight of 40,000. Enzyme treatment of A549 target plates shows that the antigen is sensitive to proteases. This MCA does not react with carcinoembryonic antigen. Patients having a variety of different lung carcinomas do not appear to have detectable antigen in their serum, nor does the antigen appear to be shed into culture supernatants by human lung carcinoma cell lines. The antigen is preserved in formalin-fixed, paraffin-embedded tissue sections and shows a cell surface and/or cytoplasmic staining pattern. Immunohistochemical staining of various bronchopulmonary carcinomas demonstrated binding to be restricted to tumors with features of "glandular" differentiation. This MCA may have clinical and diagnostic utility due to its selective binding for a subset of carcinomas of the lung.