OBJECTIVE: In this study, we firstly verified how miR-375 is downregulated in breast cancer cells with multi-drug resistance (MDR) and further investigated the regulative effect of miR-375 on Ybx1 expression.
MATERIALS AND METHODS: MiR-375 expression and promoter methylation status were studied by retrieving data in NCBI GEO Datasets, qRT-PCR and Methylation-Specific PCR (MSP) assay. Drug sensitivity of the cancer cells was assessed using MTT assay. The binding between miR-375 and YBX1 gene was predicted using Targetscan 7.1 and verified using western blot and dual luciferase assay.
RESULTS: MiR-375 is significantly downregulated in both MCF-7/ADM and MCF-7/PTX cells than in MCF-7 cells. MCF-7/ADM and MCF-7/PTX cells had significantly higher level of promoter methylation than MCF-7 cells. 5-AZA-dC treatment significantly reduced the methylation in MCF-7/ADM and MCF-7/PTX cells and increased miR-375 expression. MiR-375 can directly target 3’UTR of YBX1 and thereby decrease its expression in MCF-7/ADM and MCF-7/PTX cells. Both miR-375 overexpression and YBX1 knockdown significantly decreased P-gp expression and increased chemosensitivity of the cancer cells.
CONCLUSIONS: MiR-375 is downregulated in MCF-7/ADM and MCF-7/PTX cells, and its downregulation is a result of promoter methylation. MiR-375 can directly target 3’UTR of YBX1 and thereby decrease its expression, which might be an important mechanism of MDR in breast cancer cells.Free PDF Download
To cite this article
S.-L. Liu, Y.-F. SUI, M.-Z. Lin
MiR-375 is epigenetically downregulated due to promoter methylation and modulates multi-drug resistance in breast cancer cells via targeting YBX1
Eur Rev Med Pharmacol Sci
Vol. 20 - N. 15