MiR-34a Promotes Apoptosis and Inhibits Autophagy by Targeting HMGB1 in Acute Myeloid Leukemia Cells

Abstract

Background: MiR-34a is identified as a tumor suppressor gene and involved in acute myeloid leukemia (AML) development. However, the regulatory mechanism of miR-34a in AML is unclear. Methods: The expression of miR-34a and HMGB1 in HL-60, THP-1 and HS-5 cells were detected by qRT-PCR and western blot. Lipofectamine 2000 was used to transfect with miR-34a mimics, miR-34a inhibitor, si-HMGB1, pcDNA 3.1-HMGB1, and corresponding controls. The apoptosis and autophagy of transfected AML cells were assessed by flow cytometry and western blot, respectively. Bioinformatics software and dual luciferase reporter assay were applied to predict and verify the target of miR-34a. The effects of miR-34a mimics or si-HMGB1 on chemotherapy-induced autophagy were further explored in HL-60 cells treated with all-trans retinoic acid (ATRA) along with lysosomal protease inhibitors E64d and pepstatin A. Results: MiR-34a was lower expressed and HMGB1 mRNA and proteins were both higher expressed in HL-60 and THP-1 cells compared with that in HS-5 cells. Higher expression levels of MiR-34 and lower expression levels of HMGB1 both significantly promoted apoptosis and inhibited autophagy in HL-60 and THP-1 cells. Dual luciferase reporter system confirmed that HMGB1 was a potential target of miR-34a. Moreover, overexpression of HMGB1 dramatically reversed the promotion of apoptosis and inhibition of autophagy mediated by higher expression level of miR-34a. Higher expression level of miR-34a and lower expression level of HMGB1 both inhibited chemotherapy-induced autophagy by stimulating the LC3 conversion. Conclusion: MiR-34a promoted cell apoptosis and inhibited autophagy by targeting HMGB1. Therefore, miR-34a may be a potential promising molecular target for AML therapy.