title: Tumor-cell-induced platelet aggregation is a glycoprotein-dependent and lipoxygenase-associated process.
abstract: To characterize the platelet receptor sites and the platelet metabolic pathways involved in tumor-cell-induced platelet aggregation, we have used a homologous system consisting of human platelets and 2 tumor cell lines of human origin, which activate platelets through different mechanisms. Preincubation of platelets with an MAb against platelet glycoprotein Ib partially blocked tumor-cell-induced platelet aggregation, and preincubation of platelets with an MAb against the glycoprotein complex GPIIb/IIIa totally blocked the aggregation induced by the 2 tumor-cell lines. No inhibitory effect was found when platelets were treated with PAF-receptor antagonists or with specific peptides which block the platelet sites involved in bacterially induced platelet aggregation. Compounds which raised intra-platelet cAMP levels inhibited tumor-cell-induced platelet aggregation in a dose-related manner. Inhibition of cyclo-oxygenase by aspirin which blocked TxB2 formation by platelets did not inhibit platelet aggregation induced by tumor cells whereas the BW755 compound which inhibits cyclo- and lipoxygenase blocked platelet aggregation. These results demonstrate that tumor-cell-induced platelet aggregation is a glycoprotein-dependent and a lipoxygenase-associated phenomenon.
mesh_terms: D001241:Aspirin / Q000494:pharmacology; D002460:Cell Line; D000242:Cyclic AMP / Q000502:physiology; D011464:Epoprostenol / Q000096:biosynthesis; D006801:Humans; D008084:Lipoxygenase / Q000502:physiology*; D009369:Neoplasms / Q000503:physiopathology*; D010974:Platelet Aggregation; D010980:Platelet Membrane Glycoproteins / Q000502:physiology*; D011453:Prostaglandins / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000502:physiology; D043562:Receptors, G-Protein-Coupled
chemical_list: D010980:Platelet Membrane Glycoproteins; D011453:Prostaglandins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; D011464:Epoprostenol; D000242:Cyclic AMP; D008084:Lipoxygenase; D001241:Aspirin