Inhibitory Effect of Fibronectin and Its Recombinant Polypeptides on the Adhesion of Metastatic Melanoma Cells to Laminin

We have utilized recombinant fibronectin fragments with cell‐binding domain (C‐274), heparin‐bind‐ing domain (H‐271) or CS1 peptide in type III connecting segment (IIICS) and their fusion polypeptides such as CH‐296 (containing C‐274, H‐271 and CS1), CH‐271 (containing C‐274 and H‐271) and C‐CS1 (containing C‐274 and CS1) to investigate the mechanism of the fibronectin‐mediated inhibitory effect on tumor cell adhesion to laminin as well as fibronectin. These fragments retained cell adhesion‐promoting and/or heparin‐binding properties when they were immobilized on a surface. Pretreatment of tumor cells with CH‐296 or CH‐271 suppressed cell adhesion to both laminin and fibronectin. H‐271 at the high concentration of 500 μg/ml slightly inhibited cell adhesion to laminin (but not to fibronectin), whereas C‐274, C‐CS1 or a mixture of C‐274, H‐271 and CS1 (similar molar ratio to CH‐296) inhibited cell adhesion to fibronectin but not to laminin. On the other hand, tumor cell adhesion to laminin‐substrate was also inhibited by heparin or heparan sulfate, which were able to bind to laminin, suggesting that heparin‐like molecules on the cell surface may be included among the laminin receptors. These results indicated that the co‐presence of cell‐ and heparin‐binding domains of fibronectin may be required for the fibronectin‐mediated inhibitory effect on tumor cell adhesion to laminin, and that the interaction of the heparin‐binding domain of fibronectin with the cell surface leads to the inhibition of the cell adhesion to laminin.