Tumor thromboplastin activity In vitro

The thromboplastin activity of tissue culture media, before and after incubation with T‐241 Lewis sarcoma cells of mouse origin, or with embryonic mouse epithelial or muscle fibroblasts, was measured by means of a calcium reconstitution assay. Incubation of the embryonic epithelial or muscle fibroblasts increased the thromboplastin activity of the tissue culture media more than did incubation with tumor cells, even though analysis of protein showed that there were more tumor cells than normal cells present at the time of incubation. It is concluded that there is no evidence for a unique “Cancer Coagulative Factor” at least in this system. In vitro studies of the effect of trauma in increasing the release of thromboplastin activity from both normal and tumor tissues, suggest that the mutual destruction of both tissues could account for the elevated levels observed in some patients with cancer.