Importance of carbohydrates in platelets-mediated cell adhesion

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Mouse colon carcinoma (colon 26) cells were shown to attach to cultured hepatic sinusoidal endothelial cells only in the presence of PRP (platelet-rich-plasma). Most of tumor cells firstly attached to the endothelial cells not directly but via aggregated platelets. In addition, almost all of the tumor cells that were attached to the endothelial cells showed positive staining with ECA (Erythrina crystagalli agglutinin), whereas nearly half of the cells before adhesion were negative for ECA binding. ECA-positive cells, when separated from ECA-negative ones, revealed strong potency for metastasis to the liver compared with ECA-negative ones. ECA-positive materials were extracted from the crude membrane fraction of colon 26 cells and were found to suppress the platelet adhesion. These results indicate that the ECA-positive sugar chains on the surface of colon 26 cells should mediate the binding between colon 26 cells and platelets and the attachment of tumor cells to the endothelium. The attachment of colon carcinoma cells to hepatic sinusoidal cells induced as above may cause the successive events in establishing cancer metastasis.