rhodostomin and glycyl-arginyl-glycyl-aspartyl-serine

MCF-7 cells, a metastatic human breast carcinoma line, caused dose-dependent platelet aggregation in heparinized human platelet-rich plasma (PRP). MCF-7 tumor cell-induced platelet aggregation (TCIPA) was almost blocked by apyrase (0.5 U/ml) and completely inhibited by hirudin (5 U/ml). This TCIPA was unaffected by cysteine proteinase inhibition with E-64 (10 microM), but was limited by cell pretreatment with phospholipase A2. MCF-7 cell suspension caused marked, dose-dependent decrease in plasma recalcification times using normal, Factor VIII-deficient, and Factor IX-deficient human plasma. This effect was potentiated in cell lysates but was inhibited in intact cells preincubated with sphingosine. MCF-7 cell suspension did not affect the recalcification time of Factor VII-deficient plasma. Taken together, these data suggest that MCF-7 TCIPA arises from MCF-7 tissue factor activity expression. Trigramim and rhodostomin, RGD-containing snake venom peptides which antagonized the binding of fibrinogen to platelet membrane glycoprotein IIb/IIIa, prevented MCF-7 TCIPA. Likewise, synthetic peptide GRGDS as well as monoclonal antibodies against human tissue factor, platelet membrane glycoprotein IIb/IIIa and Ib prevented MCF-7 TCIPA, which was unaffected by control peptide GRGES. On a molar basis, trigramin (IC50, 0.1 microM) and rhodostomin (IC50, 0.03 microM), were about 5,000 and 18,000 times, respectively, more potent than GRGDS (IC50, 0.54 mM).

Topics: Adenocarcinoma; Animals; Antibodies, Monoclonal; Apyrase; Breast Neoplasms; Crotalid Venoms; Cysteine Proteinase Inhibitors; Female; Hirudins; Humans; Intercellular Signaling Peptides and Proteins; Oligopeptides; Peptides; Phospholipases A; Phospholipases A2; Platelet Aggregation; Platelet Aggregation Inhibitors; Sphingosine; Tumor Cells, Cultured

Saos-2 cells, derived from a primary human osteosarcoma, caused dose-dependent platelet aggregation in heparinised human platelet-rich plasma. Saos-2 tumour cell-induced platelet aggregation (TCIPA) was completely inhibited by hirudin but unaffected by apyrase. The cell 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 alpha v beta 3, alpha 5 beta 1 and alpha 6 beta 1 were present 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 1000 times, respectively, more potent than GRGDS in inhibiting TCIPA and tumour cell adhesion.

Topics: Amino Acid Sequence; Antibodies, Monoclonal; Apyrase; Blood Coagulation Disorders; Blood Coagulation Factors; Bone Neoplasms; Cell Adhesion; Enzyme Activation; Extracellular Matrix; Hirudins; Humans; Integrins; Molecular Sequence Data; Neoplasm Metastasis; Neoplasm Proteins; Oligopeptides; Osteosarcoma; Peptides; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Membrane Glycoproteins; Protein Binding; Thrombin; Tumor Cells, Cultured

We investigated the adhesion of human umbilical vein endothelial cells (HUVECs) to fibrin(ogen) molecule of varying structure for identifying sites that mediate cell attachment. Fibrin was prepared either with ancrod which liberates only FPA from fibrinogen, or with thrombin, which liberates both FPA and FPB. Both fibrin preparations equally supported HUVEC attachment. GRGDS, RGD-containing peptides of snake venoms, and monoclonal antibodies against alpha v beta 3 (23C6 and 7E3) inhibited the attachment of HUVECs to fibrin by 65-75%. In contrast, the attachment of HUVECs to fibrinogen was less effective and was almost completely inhibited by both RGD-containing peptides and by antibodies against integrin alpha v beta 3 (85-95% inhibition). The C-terminal dodecapeptide of fibrinogen gamma chain (residues 400-411) inhibited minimally the attachment of HUVECs to fibrin. Additionally, the binding of RGD-containing snake venom peptides to HUVECs was both RGD- and divalent-cation-dependent. The IC50S for inhibition of HUVEC attachment to fibrin were 0.09 microM (rhodostomin), 1.54 microM (trigramin) and 1.64 microM (halysin). These results indicate that fibrin mediated support of cell attachment is independent of the cleavage of FPB from fibrinogen. HUVEC attachment to fibrinogen was almost completely inhibited by RGD-containing peptides and by antibodies against alpha v beta 3. In contrast, the attachment to fibrin was partially resistant to RGD-containing peptides and to the monoclonal antibodies against integrin alpha v beta 3. However, alpha v beta 3 is the major receptor mediating HUVEC attachment to fibrin.

Topics: Amino Acid Sequence; Cell Adhesion; Cells, Cultured; Crotalid Venoms; Endothelium, Vascular; Fibrin; Fibrinogen; Humans; Intercellular Signaling Peptides and Proteins; Molecular Sequence Data; Oligopeptides; Peptide Fragments; Peptides; Receptors, Vitronectin; Snake Venoms; Umbilical Veins