ABSTRACT
<p><b>BACKGROUND</b>Most patients with acute myelogenous leukemia (AML) suffer from disordered hemostasis. We have previously shown that annexin II (Ann II), a high-affinity co-receptor for plasminogen/tissue plasminogen activator, plays a central role in primary hyperfibrinolysis in patients with acute promyelocytic leukemia (APL). The expression of Ann II in cells from patients with major subtypes of AML and the effect of arsenic trioxide (As2O3) on Ann II expression in AML cells were investigated to determine whether As2O3-mediated downregulation of Ann II could restore hemostatic stability.</p><p><b>METHODS</b>A total of 103 patients (48 females and 55 males; age, 19 - 58 years) were included. Plasma samples were collected before and after treatment as well as after complete remission. Ann II and plasminogen activation were measured in leukemic cells during treatment with 1 micromol/L As2O3.</p><p><b>RESULTS</b>Before As2O3 treatment, Ann II mRNA expression (real-time PCR) was the highest in M3 cells (P < 0.05), higher in M5 cells than that in M1, M2, M4, and M6 cells (P < 0.001), and positively correlated with Ann II protein expression (flow cytometry) (r = 0.752, P < 0.01). Exposure for up to 120 hours to As2O3 (1 micromol/L) had no significant effect on Ann II protein in M1 and M2 leukemic cells, but decreased Ann II protein expression twofold within 48 hours of exposure in M3 cells (P < 0.05) and twofold within 96 hours in M5 cells (P < 0.05). The rate of plasmin generation was higher in APL, M5, and M4 cells than in M1, M2, and M6 cells.</p><p><b>CONCLUSIONS</b>As2O3 may reduce hyperfibrinolysis in AML by downregulation of Ann II. Furthermore, As2O3 affects more than one form of AML (APL, M4 and M5), suggesting its potential role in their management.</p>