Summary
Acute promyelocytic leukaemia (APL) confers an increased risk of thrombosis and bleeding.
Current treatments are insufficient to inhibit these complications. We recently showed
that a combined immunoinhibitory and immunostimulatory short interference (si) RNA
effectively inhibited leukaemic growth and metastasis in rats with APL. We now asked
if the reported anti-leukaemic effects of siRNA treatment could be explained by inhibition
of hypercoagulability. We measured markers of coagulation and fibrinolysis in plasma
collected from APL rats with overt leukaemia using conventional assays. Coagulopathy
developed in untreated leukaemic rats evidenced by increase in several haemostatic
markers. Treatment of leukaemic rats with the siRNA reduced (p < 0.05) the concentration
of thrombin-anti-thrombin complex (a marker of coagulation) by 40% compared with rats
treated with an inactive, control siRNA. Substantial reductions (p < 0.05) were also
obtained for two markers of fibrinolysis: D-dimer (72%) and plasminogen activator
inhibitor type 1 (51%). The activity of tissue factor, the main initiator of coagulation,
was not increased (p > 0.05) in untreated leukaemic rats compared with healthy rats,
and did not change (p > 0.05) upon treatment with the siRNA. The bifunctional siRNA
reduces the hypercoagulable state in APL in addition to its direct anti-leukaemic
properties, supporting testing of this small molecule in human APL.
Keywords
Acute myeloid leukaemia - coagulopathy - rat - short interference RNA