Investigation of miR-145 target genes in multiple myeloma cell lines

Reduced expression of miR-145, a well-known tumor suppressor microRNA, directly or indirectly affects a large number of proto-oncogenes in cancer cells. It is known that decreased miR-145 expression in tumors contributes to carcinogenesis processes by targeting various genes, including JAG1, CDK4 and CDK6.In this study, we aimed at investigating the involvement of miR-145 and JAG1, CDK4 and CDK6, which are direct targets of miR-145, by performing functional studies on RPMI8226 and U266 multiple myeloma (MM) cell lines. We initially transfected miR-145 to those cells and explored the effect of ectopic miR-145 expression on cell proliferation using WST-8 technique. We then evaluated the expressions of JAG1, CDK4 and CDK6, as well as certain epithelial mesenchymal transition (EMT) markers upon miR-145 transfection with quantitative real-time PCR. A significant decrease was observed in cell proliferation capacity of miR-145 transfected cells when compared to the control group cells. Expression level of JAG1 was significantly reduced in miR-145 transfected cells compared to control group cells, although no significant alteration was found in the expressions of CDK4 and CDK6. According to the literature, JAG1, a ligand of the Notch signal pathway, is known to have increased expression in many cancers, including MM. In addition, it is thought that the over-expression of JAG1 could have an important role in the transition from monoclonal gammopathy of undetermined significance (MGUS) to MM, therefore JAG1 may serve as a marker for prediction of poor prognosis and metastasis in this cancer type. Several studies have shown that JAG1 is targeted by miR-145, however this is the first study about the relationship between miR-145 and JAG1 in MM cell lines.We would like to share our study results and our experiences as an oral presentation on functional studies about miRNAs and their target genes in the cell culture models