Role of tissue factor in the antitumor effect of recombinant human tumor necrosis factor-alpha in mice.

Recombinant tumor necrosis factor-alpha (rTNF-alpha) inhibited tumor growth of Meth A fibrosarcoma (Meth A) solid tumor in mice, and the antitumor effect of rTNF-alpha was significantly decreased by pretreatment with small doses or rTNF-alpha in mice. In in vitro experiments, incubation of human umbilical vein endothelial cells with rTNF-alpha enhanced procoagulant activity (PCA), which was drastically augmented after an addition of the conditioned medium of Meth A tumor cells. Furthermore, rTNF-alpha-induced PCA was decreased by pretreatment with rTNF-alpha in endothelial cells. This PCA was completely blocked after the addition of anti-human tissue factor (TF) murine monoclonal antibody. These results imply that in vivo antitumor effects of rTNF-alpha are mediated by expression of TF in endothelial cells, which is augmented by tumor released factor(s).