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-GMl monoclonal antibodies, AGM-1, -2, and -3, of the IgM class were produced by the immunization of BALB/c mice with ganglioside GMl inserted into liposomes with Salmonella minnesota R595 lipopolysaccharides and fusion of the spleen cells with a mouse myeloma cell line. The specificities of the monoclonal antibodies obtained were elucidated through complement-dependent liposome immune lysis assay and enzyme immunostaining on thin-layer chromatograms. All of the monoclonal antibodies reacted only with ganglioside GMl, and structurally related glycosphingolipids, such as fucosyl-GMl, asialo-GMl, GM2, and GDlb, and the other gangliosides (GM3 and GDla) tested showed no reactivity to the 3 monoclonal antibodies. These findings suggest that the monoclonal antibodies obtained may be specific for ganglioside GMl. These anti-GMl monoclonal antibodies were used to define the expression of ganglioside GMl on small cell lung carcinoma (SCLC) cell lines and tissues. In flow cytometric analysis and immunostaining studies, we observed that ganglioside GMl was highly expressed on the SCLC cell lines. Results obtained with flow cytometry and immunohistochemistry agreed well with the immunochemical determination of ganglioside GMl in lipid extracts of cell lines. Furthermore, expression of ganglioside GMl in tumor tissues from patients with SCLC was ascertained by the immunohistochemical examination of acetone-fixed paraffin-embedded tissue sections. Ganglioside GMl was detected in 5 of 19 SCLC tissues. These results suggest that ganglioside GMl is expressed in SCLC cells.