miR-181d/RBP2/NF-κB p65 Feedback Loop Promotes Chronic Myeloid Leukemia Blast Crisis

Abstract Background: Chronic myeloid leukemia (CML) is a malignant clonal proliferative disease. Once it progresses into the phase of blast crisis (CML-BP), the curative effect is poor, and the fatality rate is extremely high. Therefore, it is becoming urgent to explore the molecular mechanisms of blast crisis transition and develop new therapeutic targets.Methods: The expression levels of miR-181d, RBP2 and NF-κB p65 were assessed in 42 newly diagnosed CML-CP patients and 15 CML-BP patients. Quantitative real-time PCR, Western blots, and cell proliferation assay were used to characterize the changes induced by overexpression or inhibition of miR-181d or RBP2 or p65. Luciferase reporter assay and CHIP assay was conducted to establish functional association between miR-181d, RBP2 and p65. Inhibition of miR-181d expression and its consequences in tumor growth was demonstrated in vivo models.Results: We found that the non-coding RNA miR-181d is overexpressed in CML-BP, which promotes leukemia cell proliferation. We identified histone demethylase RBP2 as directly downregulated by miR-181d and found that RBP2 inhibited p65 expression in leukemia cells by its binding to the p65 promoter and demethylating the tri/dimethylated H3K4 region in the p65 promoter locus. Conversely, p65 directly binds to miR-181d promoter and upregulates its expression; thus, forming a positive feedback loop.Conclusions: Taken together, the miR-181d/RBP2/p65 loop promotes CML blast transformation.