The disintegrin eristostatin interferes with integrin α4β1 function and with experimental metastasis of human melanoma cells

Peptides containing the integrin recognition sequence, RGD, call inhibit experimental metastasis of mouse melanoma cells, but the. integrin(s) affected in these experiments is unknown, Besides "classical" RGD-binding integrins such as alpha 5 beta 1 and alpha v beta 3, RGD has been reported to bind alpha 4 beta 1, and mAbs to alpha 4 beta 1 can inhibit melanoma metastasis, We investigated the mode of action of the disintegrin eristostatin, an RGD-containing peptide isolated from snake venom, in a human melanoma experimental metastasis model, Lung colonization following i.v. injection of MV3 cells in nude mice was strongly inhibited by eristostatin. MV3 cells bound FITC-eristostatin and adhered to aristostatin-coated wells, This adhesion was partially inhibited by a GRGDSP peptide and by alpha 4 mAb. finding of FITC-eristostatin to Jurkat cells and adhesion of Jurkat (but not K562) cells to eristostatin-coated wells further suggested that eristostatin binds alpha 4 beta 1, even though, again, alpha 4 mAb only partially inhibited adhesion, Expression of alpha 4 beta 1 was enhanced in metastatic melanoma cells compared to normal melanocytes and nonmetastatic melanoma cells, Finally, eristostatin inhibited adhesion of both MV3 and CHO alpha 4 cells to the alpha 4 beta 1-ligand VCAM-1, while adhesion to other ligands via other integrins was not affected, These findings demonstrate that inhibition of melanoma cell metastasis by RGD-containing peptides such as eristostatin, may be due to interference with alpha 4 beta 1-VCAM binding, in addition to inhibition of the classical RGD-binding integrins. (C) 1998 Academic Press.