POSSIBLE INVOLVEMENT OF TUMOR-CELL MEMBRANE GANGLIOSIDES IN PLATELET-TUMOR CELL-INTERACTIONS

The possible correlation(s) between platelet proaggregating activity, and sialic acid content and ganglioside expression of six human colore ctal tumour cell lines (CBS, GEO, HT-29, WiDr, MIP and DLD-1) was eval uated. The three cell lines (HT-29, WiDr and DLD-1) capable of inducin g remarkable in vitro platelet aggregation, had significantly higher a mounts of lipid-bound sialic acid than those cell lines characterised by a lower platelet proaggregating activity (GEO, CBS and MIP). High p erformance thin-layer chromatography demonstrated the presence of one band comigrating with GM3 in all cell lines, while GD1a and GT1b comig rating gangliosides were present only in HT-29, WiDr and DLD-1 cells. Finally, an increased platelet pro-aggregating activity of GEO and CBS cell lines was observed after the incorporation of exogenous ganglios ides. The present data support the hypothesis that lipid-bound sialic acid may be involved in platelet-tumour cell interactions.