The Arg-Gly-Asp-containing peptide, rhodostomin, inhibits in vitro cell adhesion to extracellular matrices and platelet aggregation caused by Saos -2 human osteosarcoma cells

Abstract

Saos-2 cells, derived from a primary human osteosarcoma, caused dose-dependent platelet aggregation in heparinized human platelet-rich plasma. Saos-2 tumour cell-induced platelet aggregation (TCIPA) was completely inhibited by hirudin but unaffected by apyrase. The cells suspension shortened the plasma recalcification times of normal, factor VIII-deficient and factor IX- deficient human plasmas in a dose- dependent manner. However , the cell suspension did not affect the recalcification time of factor VII-deficient plasma. Moreover, a monoclonal antibody(MAb) against human tissue factor completely abolished TCIPA. Flow cytometric analysis using anti- integrin MAbs as the primary binding ligands demonstrated that the integrin receptors αvβ3, α5β1 and α6β1 were present on the surface of Saos -2 cells, which might mediate tumour cell adhesion to extracellular matrix. Rhodostomin, an Arg- Gly-Asp(RGD)-containing snake venom peptide which antagonises the binding of fibrinogen to platelet membrane glycoprotein IIb/IIIa, prevented Saos-2 TCIPA as well as tumour cell adhesion to vitronectin, fibronectin and collagen type I. Likewise, the synthetic peptide Gly-Arg-Gly-Asp-Ser (GRGDS) showed a similar effect. On a molar basis, rhodostomin was about 18, 000 and 1,000 times, respectively, more potent than GRGDS in inhibiting TCIPA and tumour cell adhesion.#2046#