Mesenchymal Stem Cell-Derived Exosomal miRNA-222-3p Increases Th1/Th2 Ratio and Promotes Apoptosis of Acute Myeloid Leukemia Cells.

Interferon regulatory factor 2 (IRF2) participates in the differentiation of immune T cells. Bone marrow mesenchymal stem cell (BM-MSC)-derived exosomes can secret mRNA, miRNAs, and proteins to regulate tumor microenvironment. The present study focused on the miRNA/IRF2 axis in regulating Th1/Th2 ratio and cell apoptosis in acute myeloid leukemia (AML). The flow cytometry analysis was performed to examine the Th1/Th2 ratio and AML apoptosis in vivo and in vitro. The contents of Interferon γ (IFN-γ) and Interleukin-4 (IL-4) were measured using enzyme-linked immunosorbent assay. StarBase was used to predict the potential binding site between miR-222-3p and the 3' untranslated region of IRF2. Luciferase reporter assay was applied for validating the combination of miR-222-3p and IRF2. BM-MSC exosomes were successfully isolated. BM-MSC exosomes increased Th1/Th2 ratio and promoted apoptosis of AML cells. Further analysis showed that IRF2 was targeted by miR-222-3p. Overexpression of miR-222-3p promoted Th1/Th2 ratio and AML cell apoptosis. IRF2 partially reversed the effect that is exerted by miR-222-3p on Th1/Th2 ratio and AML cell apoptosis. Overexpression of miR-222-3p promoted Th1/Th2 ratio and caspase 3 expression in vivo. To sum up, miR-222-3p promotes Th1/Th2 ratio and AML cell apoptosis by regulating IRF2 expression, which provided crucial targets for the treatment of AML.