Mechanisms of Platelet Aggregation by Murine Tumor Cell Sheddings

Abstract

Cells from a variety of animal and human neoplasms can induce the aggregation of platelets in plasma (1–3). While the mechanism of this effect has not been fully elucidated preliminary evidence suggests that several mechanisms may exist. With human tumor cells platelet aggregation may be induced via mechanisms involving the leakage of tumor cell ADP (2, 4, 5; see also Chapters 11 and 12). In rodents aggregation may occur with both whole cells and cell sheddings. This suggests that the aggregating activity of intact cells is mediated by the spontaneous release of some subcellular component. We found that a mixture of membrane vesicles and cytoplasmic dense granules were shed (6). Normal cells are also capable of shedding a small amount of material which is much less active in platelet aggregation (6,7).