Monocyte procoagulant activity as a peripheral marker of clotting activation in cancer patients.

Peripheral blood monocytes generate the procoagulant tissue factor in vitro and in vivo in response to stimulation by a variety of agents. Monocytes from cancer patients generate significantly increased tissue factor and a quantitative relationship exists between the levels of monocyte tissue factor (MTF) and levels of circulating fibrinopeptide A (FPA), a marker of in vivo clotting activation. Furthermore, monocytes from cancer patients have a greater procoagulant response to stimulation by endotoxin in vitro, which appears independent of lymphocyte regulation. These findings suggest a priming process in vivo, and may reflect exposure of monocytes to tumor antigen(s) or components of the immune response to tumors.