[Changes in the structure of fibronectin glycans caused by the transformation of BHK21/C13 cells induced by hamster sarcoma viruses. Hypothesis concerning metastatic diffusion by masking lectin sites of fibronectin].

Transformation of BHK21/C13 cells by the hamster sarcoma virus induces dramatic modifications of glycans of the N-acetyllactosaminic type from fibronectin secreted in the culture medium. In fact, the ratio tri + tetraantennary glycans/biantennary glycans increases from 0.73 to 2.46. Moreover, the fibronectin is enriched in sialic acid due to the increase of di-, tri- and tetrasialylated glycans. An hypothesis is proposed concerning the mechanism of metastasis on the basis of the knowledge we have now of the spatial conformation of glycans. In fact, tri- and tetraantennary glycans, in adopting an extended conformation called "umbrella-conformation", firmly maintained by ionic bonds between sialic acid and basic amino acid residues, cover large area of the protein. The enrichment of fibronectin from cancerous cells in tri- and tetraantennary glycans and, in the same time, in sialic acid could be related: (i) to the decrease or loss of reactivity of the protein moiety of fibronectin by masking the lectin sites and (ii) to the disappearance of fibronectin from cancer tissues and, consequently, (iii) to the mechanism of the metastasis itself.