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  • Title: Characterization of platelet aggregation induced by human breast carcinoma and its inhibition by snake venom peptides, trigramin and rhodostomin.
    Author: Chiang HS, Swaim MW, Huang TF.
    Journal: Breast Cancer Res Treat; 1995 Mar; 33(3):225-35. PubMed ID: 7749150.
    Abstract:
    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).
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