The metastatic thrombus

This video shows the formation of a metastatic thrombus. Tissue Factor (TF) in the cell membrane of the tumor cells activates factor VII, which in turn activates factor X in association with factor V, calcium-ions and phospholipids (e.g. from platelets). Active factor X catalyzes the conversion of factor II (prothrombin) into factor IIa (thrombin). Thrombin catalyzes the formation of fibrin from fibrinogen. Thrombin binds to receptors on platelets, which are then activated. Activation of the platelets changes the conformation of the aIIbb3 integrin in such a way that fibrinogen is bound. Fibrinogen also binds to avb3 integrin of the tumor cell. As a result of the bridging of platelets and tumor cells by fibrinogen, a metastatic thrombus forms, which is cross-linked by fibrin. The thrombus is further stabilized by binding of P-selectin to glycans (G) of the tumor cell.