Set9, NF-κB, and microRNA-21 mediate berberine-induced apoptosis of human multiple myeloma cells.

Aim: To investigate the mechanisms by which berberine suppressed the proliferation of human multiple myeloma cells.

Methods: Human U266 multiple myeloma cell line was tested. Cell proliferation, apoptosis, ultramicrostructure and secretion function were examined using Cell Counting Kit-8 (CCK8), flow cytometry (FCM), electron and fluorescence microscopy, as well as ELISA assay. The microRNAs (miRs) and transcription factors in U266 cells were detected using arrays and verified by qRT-PCR. EMSA and luciferase assays were used to verify the p65-dependent transactivation of miR-21 gene.

Results: Treatment of U266 cells with berberine (40-160 μmol/L) suppressed cell proliferation and IL-6 secretion in dose- and time-dependent manners. Meanwhile, berberine dose-dependently induced ROS generation, G(2)/M phase arrest and apoptosis in U266 cells, and decreased the levels of miR-21 and Bcl-2. Overexpression of miR-21 counteracted berberine-induced suppression of cell proliferation and IL-6 secretion. In U266 cells treated with berberine (80 μmol/L), the activity of NF-κB was decreased by approximately 50%, followed by significant reduction of miR-21 level. berberine (80-160 μmol/L) increased the level of Set9 (lysine methyltransferase) by more than 2-fold, caused methylation of the RelA subunit, which inhibited NF-κB nuclear translocation and miR-21 transcription. In U266 cells treated with berberine (80 μmol/L), knockdown of Set9 with siRNAs significantly increased NF-κB protein level accompanying with a partial recovery of proliferation.

Conclusion: In U266 cells, berberine suppresses NF-κB nuclear translocation via Set9-mediated lysine methylation, leads to decrease in the levels miR21 and Bcl-2, which induces ROS generation and apoptosis.