SHEDDING OF GANGLIOSIDES BY HUMAN MEDULLOBLASTOMA CELLS

Shedding of immunosuppressive gangliosides is an important characteris tic of both experimental and human tumors. Using a medulloblastoma cel l line, Daoy, with a very high ganglioside expression (141 +/- 13 nmol /10(8) cells) and a well-characterized ganglioside complement, we have now studied ganglioside shedding by human brain tumor cells. Shedding of gangliosides, quantified by metabolic radiolabeling, was significa nt (169 pmol/10(8) cells/h) and was generalized with respect to the ma jor ganglioside carbohydrate structures (G(M2), G(M3), and G(D1a)). Fo r each ganglioside, however, shedding was selective for ceramide struc tures containing shorter fatty acyl chains. Rapid and ceramide-selecti ve shedding was confirmed in two additional human medulloblastoma cell lines, D341 Med and D283 Med (112 and 59 pmol/10(8) cells/h). Signifi cant ganglioside shedding is therefore a common characteristic of huma n medulloblastoma cells and may influence the biological behavior of t his tumor, in view of immunosuppressive and other biological propertie s of shed gangliosides. (C) 1997 Academic Press.