Effect of tumor necrosis factor on the human fibrinolytic system

We report the effects on the fibrinolytic system of intravenous (IV) recombinant tumor necrosis factor-alpha (rTNF-alpha) infusions in patients with advanced cancers. During a phase I clinical trial of rTNF-alpha, the plasma fibrinolytic system was closely monitored, measuring tissue-type plasminogen activator (tPA) antigen, plasminogen activator (PA) inhibitor activity, and plasma fibrinolytic activity. Thirteen patients with refractory malignancies received 40, 80, or 160 micrograms/m2 rTNF-alpha as 2-hour IV infusions. After a 1-week rest, the same dose was repeated daily for 5 days every 3 weeks for a maximum of four courses. The serum rTNF-alpha levels peaked at the completion of the IV infusion and rapidly declined thereafter, becoming unmeasurable within 1 hour in all patients. rTNF-alpha infusion markedly alters the plasma fibrinolytic system. During the 2-hour infusion, significant increases in the tPA antigen and plasma fibrinolytic activity were seen. After the infusion, PA inhibitor activity increased, neutralizing the plasma fibrinolytic activity. The increase in PA inhibitor activity was maximal 6 hours after the onset of the rTNF-alpha infusion. Fibrinolytic properties returned to pretreatment values within 24 hours. Daily rTNF-alpha infusions caused changes in plasma tPA antigen and PA inhibitor similar to those of single infusions. We conclude from these observations that the administration of rTNF-alpha in vivo to cancer patients causes profound alterations of endothelial cell-derived components of the fibrinolytic system.