Upregulated microRNA-146a expression induced by granulocyte colony-stimulating factor enhanced low-dosage chemotherapy response in aged acute myeloid leukemia patients.

The selection of chemotherapy regimen for elderly patients with acute myeloid leukemia (AML) remains challenging. Here, we report that granulocyte colony-stimulating factor (G-CSF) upregulates the expression of microRNA (miR)-146a in a nuclear factor kappaB-dependent manner, leading to direct decreases in the expression of the target proteins CXCR4 and Smad4 in AML cells in vitro. The reduction in CXCR4 expression suppressed the migration abilities of leukemia cells. Downregulation of Smad4 promoted cell cycle entry in leukemia cells. Furthermore, an increase in apoptosis was observed when leukemia cells were treated sequentially with G-CSF and cytosine arabinoside in vitro. These findings suggest that G-CSF treatment may disrupt the protection of bone marrow niches from leukemia cells. In a review of data from 78 cases of primary AML, we found that a high miR-146a expression and/or upregulation of this miRNA during G-CSF priming chemotherapy was predictive of better clinical outcomes. Our findings suggest that miR-146a may be a novel biomarker for evaluating the clinical prognosis and treatment effects of a G-CSF priming protocol in elderly patients with AML.