[Biochemistry of tumor cell thrombosis: thrombin as growth hormone]

In tumor cell thrombosis thrombin does not only act as clotting enzyme but also as tissue hormone stimulating the proliferation of malignant cells indicated by an increase of cell count and thymidine uptake in cell cultures. Spontaneous and by cytostatic treatment induced decay of tumor cells induces the release of tumor cell thromboplastins which activate locally the clotting system and liberate thrombin. This local liberation of thrombin in tumor cell thrombosis stimulates again tumor cell proliferation and represents a biochemical substrate of tumor spread and growth in tumor cell thrombosis.