Exploring the role of microRNA-9-5p and microRNA-125b-5p for their therapeuticpotential in multiple myeloma

In recent years, microRNA (miRNA) aberrations have gained particular attention in cancer pathogenesis. In our previous study using global miRNA expression microarray, we identified overexpression of miR-9-5p and miR-125-5p in multiple myeloma (MM) patients. To date, the roles of miR-9-5p and miR-125-5p are not well understood and require further clarification. This study aimed to investigate the functional role of miR-9-5p and miR-125b-5p in MM by in vitro cell-based assays. Synthetic mimics or inhibitors were transfected into the KMS-28BM MM cell line using nucleofection. The relative miRNA expression level was detected using RT-qPCR. Cell proliferation was measured with MTS assay, while apoptosis was analysed by flow cytometry using Annexin V-FITC/ PI double staining technique. The study findings revealed that suppression of miR-9-5p with inhibitor decreased cell proliferation significantly, while enforced expression of miR-9-5p by synthetic mimics increased proliferation of these cells compared to the scrambled negative control (P < 0.05). Moreover, transfection of miR-9-5p inhibitor and mimic increased (P < 0.01) and decreased (P < 0.05) the proportion of early apoptotic cells, respectively. Apart from that, repression of miR-125b-5p significantly increased the number of late apoptotic cells while overexpression reduced the number of early apoptotic cells compared to the negative control (P < 0.05). Inhibition of miR-9-5p and miR-125b-5p exert apoptotic and/ or antiproliferative effects in KMS-28BM cells, suggesting their possible role in the treatment of MM.