Tissue procoagulant activity may be important in sustaining metastatic tumour growth

Hepatic veins as a site of clot formation following liver resection

Pulmonary embolism occurs more frequently after hepatectomy than previously thought but is infrequently associated with peripheral deep vein thrombosis. In this paper, we report 2 cases of postoperative hepatic vein thrombosis after liver resection. Both patients had undergone major hepatectomy of a non-cirrhotic liver largely exposing the middle hepatic vein. Clots were incidentally found in the middle hepatic vein 4 and 17 d after surgery despite routine systemic thrombo-prophylaxis with low molecular weight heparin. Coagulation of the transition plan in a context of mutation of the prothrombin gene and inflammation induced biloma were the likely predisposing conditions. Clots disappeared following curative anticoagulation. We conclude that thrombosis of hepatic veins may occur after liver resection and is a potential source of pulmonary embolism.

Rodent model of systemic mammary tumor disease by surgical removal of the spontaneously metastasizing SMT2A mammary carcinoma: inhibitory effect of the stable prostacyclin analogue cicaprost on occult metastasis

Cicaprost, a stable prostacyclin analogue, has been shown to be anti-metastatically active in a series of metastasizing rodent tumors. Start of treatment with cicaprost immediately before tumor implantation was a characteristic feature of our previous investigations. We have reported that in rats bearing mammary-fat-pad-implanted SMT2A mammary carcinoma, cicaprost treatment starting before tumor implantation led to a strong decrease in the number of lung metastases. In order to determine the effect on occult tumor metastasis, the present study examined the effect of starting treatment when tumor metastasis is already present. Cicaprost in daily oral doses of 0.1 mg/kg given from day 10 to day 32 reduced the number of lung metastases by about 75% compared with the control, whereas surgical removal of palpable primary tumors on day 5 or day 10 failed to influence lung metastasis. Using different treatment schedules, a pronounced reduction of the number of lung metastases was achieved by administration of cicaprost until the end of the experiment (from day 5 to day 35), whereas short-term treatments (from day 5 to day 15 or to day 25) were without significant effect. In rats whose SMT2A tumors were surgically removed 10 days after tumor implantation, there was a strong decrease of lung metastases by cicaprost given from day 20 to day 36. In addition to its inhibitory potential in animals with advanced tumor disease, cicaprost showed anti-metastatic action when used in peri-operative treatment of animals whose primary tumors had been removed. In conclusion, the present results demonstrate that cicaprost exhibits strong anti-metastatic activity in the SMT2A rat mammary-carcinoma model with treatment started when occult tumor metastases are already present. Results also indicate that direct effects on tumor cells may contribute to the anti-metastatic action of cicaprost in spontaneously metastasizing tumors.

Tumor spheroid-induced vesicle formation on endothelial cells is associated with procoagulant properties

Fibrin deposits in tumor beds are an intriguing phenomenon. It has been suggested that fibrin plays a role as a provisional matrix in which the tumor grows and induces development of a vascular network. On the other hand fibrin possibly protects the tumor nodule from host defense mechanisms. We therefore investigate whether tumor cells can induce a procoagulant response in endothelial cells leading to fibrin formation. For our studies we employed a modification of the matrix model of Montesano in which sprouting of endothelial cell aggregates can be followed. This system allows us to study in vitro the involvement of coagulation in tumor growth and angiogenesis. Cocultures of endothelial cell aggregates and avascular tumor spheroids in collagen type I gels results in the appearance of extracellular vesicle-like structures on the endothelial sprouts. The vesicles formed on endothelial cell sprouts upon coculturing with tumor cells exhibit an increased amidolytic activity, suggestive of factor X/Xa activity, not dependent on tissue factor exposure. Experiments using HgCl2 and Iodoacetamide point to the importance of SH groups in the factor X/Xa activity on endothelial cell sprouts.