HUMAN MEDULLOBLASTOMA GANGLIOSIDES

To establish a model system for the study of ganglioside metabolism of the human brain tumor, medulloblastoma, we have chemically characteri zed the gangliosides of the Daoy cell line, These cells contain a high concentration of gangliosides (143 +/- 13 nmol LBSA/10(8) cells), The major species have been structurally confirmed to be G(m2) (65.9%), G (m3) (13.0%), and G(d1a) (10.3%), Isolation of individual gangliosides homogeneous in both carbohydrate and ceramide moieties by reversed-ph ase HPLC and analysis by negative-ion fast atom bombardment collisiona lly activated dissociation tandem mass spectrometry have allowed us to unequivocally characterize ceramide structures, In the case of G(m2), 10 major ceramide subspecies were identified: d18:1-hC16:0, d18:1-C16 :0, d18:0-C16:0, d18:1-C18:0, d18:1-C20:0, d18:1-C22:0, d18:2-C24:1, d 18: 1-C23:1, d18:1-C24:1, and d18:1-C24:0, Taken together with previou s studies, these findings in human medulloblastoma cells support the v iew that high expression and marked heterogeneity of ceramide structur e are general characteristics of tumor gangliosides, molecules which a re shed by the tumor cells and which are biologically active in vivo.