miR-125b expression affects tumor growth of multiple myeloma via targeting MKK7

Many miRNAs are reported to be involved in tumor development. The underlying mechanism of miRNAs driving multiple myeloma (MM) progress remains elusive. This study is to investigate the effect of miR-125b, a brain-enriched microRNA, on mitogen-activated protein kinase 7 (MKK7) in vivo. We found significantly up-regulation of miR-125b and deregulation of MKK7 in MM. The inverse correlation was further confirmed in multiple myeloma samples and cell lines. In addition, MKK7 was identified as a downstream target gene of miR-125b, which could bind to the 3' UTR of MKK7. Overexpression of miR-125b was associated with decreased MKK7 expression and miR-125b antagonisminhibited cell proliferation and clonogenicity. Taken together, our results demonstrated that MKK7 could function as an important tumor suppressor neutralized by miR-125b in MM, suggesting that miR-125b may be a novel potential molecular therapeutic target in the treatment of MM.