Epigenetic deregulated miR-375 contributes to the constitutive activation of JAK2/STAT signaling in myeloproliferative neoplasm.

Constitutive activation of Janus kinase 2/signal transducers and activators of transcription (JAK2/STAT) signaling caused by JAK2V617F and other mutations is central to the pathogenesis of myeloproliferative neoplasm (MPN). Negative regulators such as suppressors of cytokine signaling (SOCS) inhibit activated JAK2/STAT signaling. However, whether silencing of negative regulators facilitates JAK2/STAT signaling is unclear. Here, we report that loss of miR-375 expression contributes to the constitutive activation of JAK2/STAT signaling. MiR-375 reduced JAK2 protein level and repressed the activity of a luciferase reporter by binding 3'-untranslated regions, which was abolished by the mutation of the predicted miR-375-binding site. Meanwhile, a significant inverse correlation between the expressions of miR-375 and JAK2 was found in multiple types of leukemic cell lines and bone marrow mononuclear cells from MPN patients, suggesting that JAK2 may be a miR-375 target gene. Furthermore, forced expression of miR-375 inhibited constitutive and inducible JAK2/STAT signaling, suppressed cell proliferation, and decreased colony formation in hematopoietic progenitors from MPN patients. Finally, histone deacetylation (HDAC) inhibitors restored miR-375 expression, which was much lower in patients with MPN compared with healthy volunteers. Collectively, our data suggest that the loss of miR-375 expression enhances the constitutive and persistent activation of JAK2/STAT signaling. Restoration of miR-375 expression might contribute to the clinical treatment for MPN patients.