MiR-21 Regulates the Proliferation of Multiple Myeloma Cells by Inhibiting the Expression of KLF5

Abstract

To study the expression of miR-21 in multiple myeloma (MM) cell lines and plasma cells of patients, and explore the mechanism of miR-21 in MM. Bone marrow samples from 30 patients with MM and 18 healthy controls were collected. The plasma cells were separated by magnetic beads. MM cell lines (MM1.S cells, RPMI-8226 cells and U266 cells) were cultured. The expression level of miR-21 was detected by real-time fluorescent quantitative PCR (qRT-PCR). After transfection with hsa-miR-21 mimics and hsa-miR-21 inhibitor, the proliferation of MM cells was detected by CCK-8 and cell cloning assay. The target genes regulated by miR-21 were predicted by bioinformatics website. The binding sites of miR-21 and KLF5 were detected by luciferase reporter gene assay. The expression of KLF5 were detected by Western blot and qRT-PCR after hsa-miR-21 mimics and hsa-miR-21 inhibitor were transfected into RPMI-8226 cells. KLF5 plasmid with 3'UTR knockout was synthesized and cotransfected into RPMI-8226 cells with hsa-miR-21 mimics, and the proliferation of MM cells was detected by CCK-8 and cell cloning assay. Compared with healthy donors, the expression level of miR-21 in plasma cells of patients with MM was significantly increased (P<0.001); the expression of miR-21 in MM cell lines MM1.S, RPMI-8226 and U266 was significantly higher than that in control group (P<0.05). After hsa-miR-21 mimics transfection, the proliferation and the number of colony formation of MM cells was significantly increased, while the proliferation and the number of colony formation of MM cells was decreased after hsa-miR-21 inhibitor transfection (P<0.01). The results of luciferase reporter gene assay showed that miR-21 could bind to 3'UTR of KLF5, and the expression level of KLF5 protein was significantly decreased after hsa-miR-21 mimics transfection. After 3'UTR-knockout KLF5 plasmid and hsa-miR-21 mimics were cotransfected into RPMI-8226 cells, the proliferation of the cells was significantly decreased. MiR-21 may be involved in regulating the proliferation of MM cells by inhibiting the expression of KLF5.