Overexpression of MIR9 indicates poor prognosis in acute lymphoblastic leukemia

Aberrant expression of MIR9 predicts a poor prognosis in acute myelogenous leukemia. To evaluate its clinical significance in acute lymphoblastic leukemia, we analyzed expression levels of MIR9 in bone marrow samples from patients with acute lymphoblastic leukemia and compared them to those in normal bone marrow cells. Approximately 20% of them showed higher expression compared with controls. There was a tendency that patients who showed overexpression of MIR9 underwent worse clinical courses, but without statistical significance. However, when the analyses were restricted to patients who did not receive a stem cell transplant, overexpression of MIR9 was significantly associated with worse overall survival. Interestingly, exaggerated MIR9 expression and higher white blood cell count at presentation were independent unfavorable prognostic factors in all patients for overall survival by multivariate analysis. The presence of higher MIR9 expression could be a useful indicator for treatment stratification.