Recombinant human soluble thrombomodulin safely and effectively rescues acute promyelocytic leukemia patients from disseminated intravascular coagulation.

We treated individuals for disseminated intravascular coagulation (DIC) caused by acute promyelocytic leukemia (APL) (n=9) using human soluble thrombomodulin (rTM) in combination with all-trans retinoic acid (ATRA) and chemotherapy, and compared the clinical outcomes with historical control patients (n=8) treated with ATRA and/or chemotherapy. Two control patients developed intracranial vascular incidents. On the other hand, no bleeding related mortality was noted in rTM-treated patients. Notably, treatment with rTM rescued patients from DIC earlier than historical controls (log rank test, p=0.019). These results suggest that administration of rTM should be considered for the treatment of individuals with DIC associated with APL.

Thrombomodulin enhances the antifibrinolytic and antileukemic effects of all-trans retinoic acid in acute promyelocytic leukemia cells.

This study found that levels of thrombomodulin (TM) were downregulated in freshly isolated leukemia cells from patients with acute promyelocytic leukemia (APL, n = 7) and acute myelogenous leukemia (n = 14), as compared with CD34(+)/CD38(-) hematopoietic stem/progenitor cells and CD34(-)/CD33(+)/CD11b(-) promyelocytes isolated from healthy volunteers (n = 3). Exposure of APL NB4 cells to recombinant human soluble TM (rTM, 1500 ng/mL) inhibited clonogenic growth of these cells by approximately 30%, and induced expression of CD11b, a marker of myeloid differentiation, on their surfaces, in association with upregulation of nuclear levels of myeloid-specific transcription factor CCAAT/enhancer binding protein ε. These antileukemic effects of rTM were mediated by thrombin/activated protein C-dependent mechanisms, as hirudin, an inhibitor of thrombin and a blocking antibody against endothelial receptor for protein C to which activated protein C binds, hampered the ability of rTM to induce expression of CD11b in NB4 cells. This study also found that rTM downregulated expression of Annexin II, a receptor for both plasminogen and tissue plasminogen activator, and inhibited plasmin activity in APL cells. Interestingly, rTM significantly enhanced the ability of all-trans retinoic acid to induce growth arrest, differentiation and apoptosis, and inhibited plasmin activity in APL cells. Taken together, these results suggest that administration of rTM should be considered for treatment of individuals with disseminated intravascular coagulation associated with APL.

Expression of p-JAK2 predicts clinical outcome and is a potential molecular target of acute myelogenous leukemia.

Our study determined if Janus kinase 2 (JAK2) was activated in acute myelogenous leukemia (AML; n = 77, excluding acute promyelocytic leukemia) by immunohistochemistry (IHC) using a phosphor-specific antibody against JAK2. p-JAK2 was detectable in all cases, although its levels varied between patient samples (high levels, n = 31; low levels, n = 46). The quantification of levels of p-JAK2 by IHC was well correlated with that assessed by Western blot analyses and fluorescence-activated cell sorting (FACS). Levels of p-JAK2 were directly correlated with high white blood cell count (52.3 × 10(3) /L in patients with high p-JAK2 vs. 28.3 × 10(3) /L in patients with low p-JAK2, p < 0.01) and were inversely correlated with complete remission rates (45% in patients with high p-JAK2 vs. 78% in patients with low p-JAK2, p < 0.003). In addition, multivariate analysis confirmed that high levels of p-JAK2 remained a significant factor for overall survival (hazard ratio = 2.213; 95% confidence interval, 1.212-4.041, p = 0.023). Moreover, we found that AZ960, a novel and specific inhibitor of the JAK2 kinase, potently inhibited the clonogenic growth and induced apoptosis of freshly isolated AML cells from patients in association with cleavage of caspase 3 and downregulation of anti-apoptotic Bcl-xL proteins. Taken together, JAK2 may be a promising molecular target for treatment of AML.