Murine monoclonal antibody LAM2 defines cell membrane determinant with preferential expression on human lung small-cell carcinoma and squamous-cell carcinomas.

Murine monoclonal antibodies (MAbs) were generated against a human undifferentiated lung carcinoma cell line. The hybridoma designated LAM2 produced an IgM kappa MAb with reactivity to the cell membrane. Indirect immunofluorescence staining and radioimmunoassay showed LAM2 antibody to react preferentially with lung small-cell carcinoma (SCC) cell lines and squamous-cell carcinoma (SQC) cell lines. LAM2 antibody also stained primary cultures of normal bronchial epithelial cells, but was unreactive with human erythrocytes and nucleated marrow cells. Indirect immunofluorescent staining with LAM2 antibody was performed on frozen sections of human tumor tissues and normal tissues. LAM2 antibody stained all 8 SCC carcinomas, 4 of 5 SQC of the lung and head and neck region, and 2 or 4 lung large-cell carcinomas. No staining was seen on lung adenocarcinomas, breast carcinomas, ovarian carcinomas, renal cell carcinomas, colon carcinomas, or mesotheliomas. Staining was present on sections of normal bronchus, but not on normal lung parenchyma, liver, kidney, adrenal or skin. While LAM2 antibody was highly reactive with all SCC examined, its antigenic determinant was not expressed in other cell lines and tumors of presumed neuroectodermal origin, including neuroblastoma, melanoma, and bronchial carcinoid. Radioimmunoprecipitation showed the antigen defined by LAM2 antibody to have two major bands of approximate molecular weights of 45,000 and 125,000. The selective reactivity of LAM2 antibody with SCC and SQC, but not with most other tumor tissues and normal tissues, makes it a good candidate for use in clinical diagnosis and possibly serotherapy.