ESTABLISHMENT OF MONOCLONAL-ANTIBODIES SPECIFIC FOR GANGLIOSIDE GM1 -DETECTION OF GANGLIOSIDE GM1 IN SMALL-CELL LUNG-CARCINOMA CELL-LINES AND TISSUES

Three kinds of anti-GM1 monoclonal antibodies, AGM-1, -2, and -3, of t he IgM class were produced by the immunization of BALB/c mice with gan glioside GM1 inserted into liposomes with Salmonella minnesota R595 li popolysaccharides and fusion of the spleen cells with a mouse myeloma cell line. The specificities of the monoclonal antibodies obtained wer e elucidated through complement-dependent liposome immune lysis assay and enzyme immunostaining on thin-layer chromatograms. All of the mono clonal antibodies reacted only with ganglioside GM1, and structurally related glycosphingolipids, such as fucosyl-GM1, asialo-GM1, GM2, and GD1b, and the other gangliosides (GM3 and GD1a) tested showed no react ivity to the 3 monoclonal antibodies. These findings suggest that the monoclonal antibodies obtained may be specific for ganglioside GM1. Th ese anti-GM1 monoclonal antibodies were used to define the expression of ganglioside GM1 on small cell lung carcinoma (SCLC) cell lines and tissues. In flow cytometric analysis and immunostaining studies, we ob served that ganglioside GM1 was highly expressed on the SCLC cell line s. Results obtained with flow cytometry and immunohistochemistry agree d well with the immunochemical determination of ganglioside GM1 in lip id extracts of cell lines. Furthermore, expression of ganglioside GM1 in tumor tissues from patients with SCLC was ascertained by the immuno histochemical examination of acetone-fixed paraffin-embedded tissue se ctions. Ganglioside GM1 was detected in 5 of 19 SCLC tissues. These re sults suggest that ganglioside GM1 is expressed in SCLC cells.