miR-181a sensitizes resistant leukaemia HL-60/Ara-C cells to Ara-C by inducing apoptosis

Ara-C is one of the most commonly used drugs in the treatment of AML. However, the development of drug resistance always prevented its further use. It has been shown that miR-181a is associated with the clinical outcome of AML patients. Here, we investigated the possible role of miR-181a in AML Ara-C resistance. miR-181a expression was measured by real-time PCR. Cell viability was detected by MTT assay. Protein expressions were measured by western blotting. Caspase activity was examined by florescence assay. We found that miR-181a expression was downregulated in the Ara-C-resistant cell line HL-60/Ara-C compared with its parental cell line HL-60. Overexpression of miR-181a in HL-60/Ara-C cells sensitized the cells to Ara-C treatment. Furthermore, Bcl-2 was confirmed as a direct miR-181a target by immunoblot analysis and reporter gene assays. Knockdown of Bcl-2 mimicked the effect of enforced miR-181a expression by reducing cell viability. In addition, the apoptosis pathway was activated by cytochrome C release and caspase 9/caspase 3 activation after miR-181a overexpression. This study for the first time demonstrated that downregulation of miR-181a and upregulation of Bcl-2 in leukaemia cells confer resistance to Ara-C-based therapy. These results suggest that restoration of miR-181a expression might provide a promising therapeutic in drug resistance of leukaemia.