Effect of four disintegrins on the adhesive and metastatic properties of B16F10 melanoma cells in a murine model.

Four disintegrins, eristostatin, albolabrin, barbourin and echistatin, injected IV into C57BL/6 mice in combination with B16F10 murine melanoma cells, inhibited formation of experimental lung metastases with ID50s of 0.05, 1.0, 0.9, and 3.7 mumoles per mouse, respectively. When injected 1 h after tumor cells, albolabrin, echistatin and barbourin had the same antimetastatic activity, while eristostatin was not active. Eristostatin (IC50 7-8 nM) was more potent than echistatin (IC50 74-75 nM), barbourin (IC50 46-60 nM), and albolabrin (IC50 130-165 nM) as an inhibitor of murine platelet aggregation induced by ADP or tumor cells. Fibronectin was the best substrate for melanoma cell adhesion (95%), followed by laminin (47%) and vitronectin (24%). Albolabrin was the strongest and eristostatin the weakest inhibitor of cell adhesion to all substrata. Adhesion of melanoma cells to albolabrin, echistatin, and barbourin was partially inhibited by monoclonal antibody against mouse alpha v subunit. This antibody bound to B16F10 melanoma cells in suspension and inhibited binding of fluorescein isothiocyanate (FITC)-labeled disintegrins to these cells, being the most effective with FITC-labeled albolabrin. Our study suggests that a major contribution of eristostatin to inhibition of lung colonization is via preferential binding to platelet alpha IIb beta 3 integrin and blocking tumor cells interaction with platelets. A major contribution of albolabrin, barbourin and echistatin appears to be by interference with other integrin receptors on the tumor cell surface. Albolabrin appeared to inhibit RGD-dependent integrins containing alpha v subunit, such as alpha v beta 3 and alpha v beta 1.