A New Molecular Network Comprising PU.1, Interferon Regulatory Factor Proteins and MiR-342 Stimulates ATRA-mediated Granulocytic Differentiation of Acute Promyelocytic Leukemia Cells

In the acute promyelocytic leukemia (APL) bearing the t(15;17), all-trans-retinoic acid (ATRA) treatment induces granulocytic maturation and complete remission of leukemia. We identified miR-342 as one of the microRNAs (miRNAs) upregulated by ATRA during APL differentiation. This miRNA emerged as a direct transcriptional target of the critical hematopoietic transcription factors PU.1 and interferon regulatory factor (IRF)-1 and IRF-9. IRF-1 maintains miR-342 at low levels, whereas the binding of PU.1 and IRF-9 in the promoter region following retinoic ATRA-mediated differentiation, upregulates miR-342 expression. Moreover, we showed that enforced expression of miR-342 in APL cells stimulated ATRA-induced differentiation. These data identified miR-342 as a new player in the granulocytic differentiation program activated by ATRA in APL.