OBJECTIVETo study the fibrinolytic activity in patients with acute promyelocytic leukemia (APL) and its alteration in all-trans retinoic acid (ATRA) and/or arsenic trioxide (ATO) treatment.

METHODSPlasma fibrinogen concentration was determined with the conventional method, and the levels of fibrin degradation products (FDP) and D-dimer were quantified with ELISA. Plasminogen was measured by chromogenic assay. Cell surface expression of Annexin II and u-PAR and their mRNA levels were measured by flow cytometry and real time-PCR, respectively.

RESULTSThe levels of FDP and D-dimer in APL were remarkably higher in APL patients than that in normal controls, while fibrinogen and plasminogen were lower. Both Annexin II and u-PAR were highly expressed on APL cells, which declined after treatment with ATRA and/or ATO, but remained higher than those on normal bone marrow mononuclear cells.

CONCLUSIONAbnormally high levels of Annexin II and u-PAR expression on APL cells may contribute to the increased production of plasmin, leading to primary hyperfibrinolysis in APL. ATRA and ATO therapy induces down-regulation of Annexin II and u-PAR expression, which may be contribute, at least in part, to the relief of the hemorrhagic complications in APL.