HDAC2-miRNA183 Epigenetic Circuit Contributes to the Growth of Philadelphia-Positive Acute Lymphoblastic Leukemia Via BCR-ABL/PTEN/p-AKT and c-MYC Signaling Pathways

Purpose: To characterize the expression and function of leukemia related/specific microRNAs (miRNAs) in Philadelphia-positive Acute Lymphoblastic Leukemia (Ph-positive ALL), and to identify the mechanistic signaling pathways in Ph-positive ALL.

Method: Differentially expressed miRNAs in Ph-positive ALL patient samples and cell line were identified using RNA-seq and qPCR. Cell proliferation and apoptosis were detected with CCK-8 and flow cytometry assays, respectively. Bioinformatics software predicted the upstream and downstream regulatory pathway of miRNA183; the dual luciferase reporter gene analysis verified the regulatory effect of miRNA183 on the target gene BCR-ABL; ChIP experiment detected the recruitment of HDACs in the miRNA183 promoter region, and western blot detected the expression of related protein in the miRNA183 related pathway.

Results:

• We identified thirty-one differentially expressed miRNAs in three Ph-positive ALL samples vs. normal karyotype B-ALL samples. Among these alternately expressed miRNAs, we found miRNA183 was significantly downregulated in Ph-positive ALL. qPCR verified the down-expression of miRNA183 in Ph-positive ALLcasesamples and Ph-positive ALL cell line SUP-B15. Forced over-expression of miRNA183 inhibited proliferation of SUP-B15 cells, but had no effect on NALM-6 cells (normal karyotype B-ALL). Furthermore, either forced over-expression of miRNA183 or silence down of BCR-ABL1 promoted SUP-B15 cell apoptosis.

• TargetScan software prediction found that miRNA183 and BCR-ABL (e1a2) had potential binding sites, dual luciferase reporter gene experiments further proved that miRNA183 could direct bind to BCR-ABL gene; qPCR and western blot further showed that miRNA183 inhibited the expression of P190. Our results showed that BCR-ABL (e1a2) is the target gene of miRNA183. In addition, forced over-expression of miRNA183 and silence down of BCR-ABL1 regulated the downstream proteins including PTEN, PARP, p-AKT and c-MYC with the same change trend. In complementary loss-of-function studies, inhibition of miRNA183 restored the expression of these proteins.

• Treatment of SUP-B15 cells with decitabine (DAC) and histone deacetylase inhibitor (HDACi), respectively, resulted in decrease of cell viability in a dose-dependent manner. Surprisingly, miRNA183 levels were significantly increased in HDACi exposure but not in DAC exposure. Furthermore, miRNA183 inhibitor reduced HDACi-induced upregulation of miRNA183 expression and attenuated HDACi-mediated apoptosis in SUP-B15 cells. Biology software prediction showed the presence of a transcription start site (TSS) 5 kb upstream of miRNA183. ChIP assay further demonstrated that HDAC2 but not HDAC1 was specifically recruited to the miRNA183 promoter region. Additionally, after HDACi treatment, HDACi-induced H3K27ac was recruited and accumulated at the miRNA183 promoter region. Western blotassay further proved the changes of the related proteins.

Conclusion :Our results indicate that miRNA183 is a potential biomarker for Ph-positive ALL and suggest that a novel “HDAC2-miRNA183 Epigenetic Circuit” may be involved in the growth and progression of Ph-positive ALL by PTEN/p-AKT and c-MYC signaling pathways. Taken together, this study may provide novel approaches to the design of targeted drugs for Ph-positive ALL.