MiR-362-5p promotes the malignancy of chronic myelocytic leukaemia via down-regulation of GADD45α

BACKGROUND: MicroRNAs (miR, miRNAs) play pivotal roles in numerous physiological and pathophysiological contexts. We investigated whether miR-362-5p act as an oncogene in chronic myeloid leukaemia (CML) and aimed to understand its potential underlying mechanisms. METHODS: We compared the miR-362-5p expression levels between CML and non-CML cell lines, and between fresh blood samples from CML patients and normal healthy controls using quantitative real-time PCR (qPCR). Cell counting kit-8 (CCK-8) and Annexin V-FITC/PI analyses were used to measure the effects of miR-362-5p on proliferation and apoptosis, and Transwell assays were used to evaluate migration and invasion. A xenograft model was used to examine in vivo tumourigenicity. The potential target of miR-362-5p was confirmed by a luciferase reporter assay, qPCR and western blotting. Involvement of the JNK(1/2) and P38 pathways was investigated by western blotting. RESULTS: miR-362-5p was up-regulated in CML cell lines and fresh blood samples from CML patients, and was associated with Growth arrest and DNA damage-inducible (GADD)45α down-regulation. Inhibition of miR-362-5p simultaneously repressed tumour growth and up-regulated GADD45α expression in a xenograft model. Consistently, the knockdown of GADD45α expression partially neutralized the effects of miR-362-5p inhibition. Furthermore study suggested that GADD45α mediated downstream the effects of miR-362-5p, which might indirectly regulates the activation of the JNK(1/2) and P38 signalling pathways. CONCLUSION: miR-362-5p acts as an oncomiR that down-regulates GADD45α, which consequently activates the JNK(1/2) and P38 signalling. This finding provides novel insights into CML leukaemogenesis and may help identify new diagnostic and therapeutic targets. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12943-015-0465-3) contains supplementary material, which is available to authorized users.