[Expression Analysis and Epigenetics of MicroRNA-28-5p in Multiple Myeloma]

To investigate the expression, mechanism and methylation level of miR-28-5p in multiple myeloma (MM), so as to provide the expirement basis for searching new targeted therapy.

RT-PCR was used to detect the expression levels of miR-28-5p and potential target CCND1 in CD138⁺ cells of the patients with MM and bone marrow mononuclear cells of patients with iron defficiency anemia(IDA) as control, Methylation-specific PCR(MSP) was used to detect methylation levels of CpG island in LPP/miR-28-5p promoter region and the correlation with other clinical indicators was analyzed. The 5-aza-2'-deoxycytidine (5-Aza-dC，DAC) was used to treat MM cell line U266; after drug treatment，MSP was used to analyze the methylation status of the CpG islands in LPP/miR-28-5p promoter; the qPCR was used to detect the expression levels of miR-28-5p，and the regulatory mechanism of miR-28-5p expression was explored furtherly.

The methylation level of CpG island in LPP/miR-28-5p promoter region of MM patients was significantly higher than that of IDA patients. The relative expression level of miR-28-5p in MM patients was significantly lower than that of IDA patients. The relative expression level of miR-28-5p in newly diagnosed MM patients was higher than that in relapsed/progressive patients. The miR-28-5p target CCND1 was expressed at high levels in MM patients with LPP / miR-28-5p methylation, the expression level of miR-28-5p in MM patients correlated with β₂-MG concentration. 5-aza-dc could significantly inhibit the growth of U266 cell line, arrest the cell cycle in G₁ phase, inhibit the biosynthesis of cellular RNA and protein and promote cell apoptosis. At the same time, up-regulation of miR-28-5p expression was found.

The expression of miR-28-5p in MM patients is regulated by methylation of CpG islands in the promoter region of the genome.miR-28-5p may act as a tumor suppressor gene, and its low expression may be involved in the occurrence and development of MM, suggesting that miR-28-5p may become a new target for the treatment of MM.