Summary
Tissue factor (TF) and urokinase receptor (uPAR) are key cellular receptors triggering,
respectively, coagulation and fibrinolysis. Bleeding complications among leukemic
patients have been related to an abnormal expression of TF by blast cells and/or to
an abnormal fibrinolytic response. In this study the expression of TF and uPAR has
been assessed in 18 acute non-lymphoblastic and 8 lymphoblastic leukemic blast cells
using several methodological approaches. TF mRNA was evaluated by in situ hybridization
and TF and uPAR antigen were evaluated immunologically in cell lysates and on the
cell surface by flow cytometry. In addition, TF-procoagulant activity was measured
in coagulation-based assays. The reliability of these methods was corroborated in
six leukemic cell lines of different lineages and states of maturation. Disseminated
intravascular coagulation was detected in two M3 leukemia patients whose blast cells expressed high amounts of TF. Hyperfibrinolysis
was detected in one M1 and two M2 patients, whose blast cells displayed a high content of uPAR antigen, but no TF.
Furthermore, M5 leukemia blast cells expressed both TF and uPAR, although no hemostatic defects or
bleeding complications were detected in these patients. Taken together, although a
limited number of patients was included in this study, these data suggest that in
leukemia patients exhibiting bleeding, either TF or uPAR are expressed by their blast
cells. However, the presence of these receptors does not necessarily imply the existence
of a hemostatic disorder.
