TRIFLAVIN, AN ANTIPLATELET PEPTIDE, INHIBITS TUMOR CELL-EXTRACELLULARMATRIX ADHESION THROUGH AN ARGININE-GLYCINE-ASPARTIC ACID-DEPENDENT MECHANISM

The interaction of tumor cells with extracellular matrix components su ch as laminin, fibronectin, and collagen has been shown to be mediated through a family of cell-surface receptors that specifically recogniz e an arginine-glycine-aspartic acid amino acid sequence within each pr otein. Triflavin, a 7.5 kDa cysteine-rich polypeptide purified from Tr imeresurus flavoviridis snake venom, belongs to a family of arginine-g lycine-aspartic acid-containing peptides termed disintegrins that have been isolated from the venoms of various vipers and shown to be poten t inhibitors of platelet aggregation. In this study, we showed that tr iflavin inhibited adhesion of human hepatoma J-5 cells to extracellula r matrices (fibronectin, vitronectin, fibrinogen, and collagen type I) in a dose-dependent manner. On the other hand, triflavin exerted a li mited inhibitory effect on cell attachment to collagen type IV and lam inin (less than or equal to 40%). Triflavin is approximately 1000 time s more potent than glycine-arginine-glycine-aspartic acid-serine at in hibiting cell adhesion. When immobilized on plate, triflavin promoted J-5 cell attachment; this attachment was inhibited by glycine-arginine -glycine-aspartic acid-serine. In addition, triflavin labeled with iod ine 125 binds to J-5 cells in a saturable manner and its binding was a lso inhibited by glycine-arginine-glycine-aspartic acid-serine. Its K- d value was estimated to be 3.9 x 10(-7) mol/L and the number of bindi ng sites was around 60,000 per cell. Furthermore, triflavin did not af fect tritiated thymidine uptake during a 3-day incubation. These resul ts suggest that triflavin binds by means of its arginine-glycine-aspar tic acid amino acid sequence to integrin receptor expressed on the J-5 cell surface, inhibiting the adhesion of extracellular matrices to tu mor cells.