Inhibitory Effect of Antimetastatic Fusion Polypeptide of Human Fibronectin on Tumor Cell Adhesion to Extracellular Matrices

We investigated the inhibitory mechanism of liver metastasis by using recombinant fragments with cell‐ and/or heparin‐binding domains (C‐274, H‐271 or the fusion fragment CH‐271). Intravenous co‐injection of L5178Y‐ML25 cells with CH‐271 was more effective for the inhibition of liver metastasis than C‐274, H‐271 or C‐274+H‐271. Reduction of the arrest and retention of the radiolabeled tumor cells in the liver of mice was found when CH‐271 was co‐injected with tumor cells. L5178Y‐ML25 cells adhered both concentration‐ and time‐dependently to the substrates precoated with fibronetin, laminin and reconstituted basement membrane, Matrigel. The tumor cell adhesions to the substrates were inhibited in the presence of CH‐271. The tumor cell interaction with CH‐271‐substrate was inhibited by heparin, and monoclonal antibodies (IST‐1 or IST‐2) against the heparin‐binding domain of fibronectin. However, monoclonal antibodies against the cell‐binding domain failed to block the interaction. Similarly, CH‐271‐mediated antimetastatic activity was also inhibited by the treatment of CH‐271 with IST‐1 before the co‐injection with tumor cells, whereas monoclonal antibody against the cell‐binding domain had no effect. Thus, the antimetastatic effect of CH‐271 fusion fragment on liver metastasis of L5178Y‐ML25 cells may be partly due to interference with the adhesive interaction of tumor cells with extracellular matrix or basement membrane components by a heparin‐binding domain‐dependent mechanism.