Activation of blood coagulation and local
fibrin deposition may contribute to
tumor metastasis. We have examined the ability of four human tumor cell lines (COLO 205, HepG2, J82 and CAPAN-2) to augment the conversion of
prothrombin to
thrombin by
factor Xa and
calcium in the presence and absence of exogenous
factor Va. Using a
chromogenic substrate assay to assess
thrombin formation, we observed that all the above cell lines accelerated
prothrombin activation in the absence of exogenous
factor Va. The order of effectiveness was COLO 205 greater than HepG2 greater than J82 greater than CAPAN-2. In the absence of cells, no detectable
thrombin formation occurred. Pretreatment of COLO 205 and HepG2 cells with anti-human
factor V IgG inhibited
prothrombin activation in a dose-dependent manner, but was without effect in J82 and CAPAN-2 incubation mixtures.
Factor V coagulant activity was observed in COLO 205 and HepG2 cells as well as their
culture media, but was not detected in J82 and CAPAN-2 cells or their
culture media. Biosynthetic labeling and immunoprecipitation studies revealed that COLO 205 and HepG2 cells constitutively synthesized
factor V or
a factor-V-like molecule that comigrated with human
factor V/Va on
sodium dodecyl sulfate-
polyacrylamide gel electrophoresis. All four tumor cell lines exhibited saturation binding of exogenous human
factor Va resulting in a dose-dependent enhancement of their ability to augment
prothrombin activation. Our results indicate that these
tumor cells can readily assemble a functional cell surface
prothrombinase complex that may be important in
fibrin deposition associated with the growth and metastatic progression of these, and perhaps, other
tumors.