Chemotherapeutic drugs affect methylation of ER-α in breast cancer cells by down-regulating miR-148b / 中华内分泌外科杂志

ABSTRACT

Objective To investigate the effects of chemotherapeutic drugs on ER-α expression and methylation in breast cancer cells.Methods Human breast cancer cells MCF-7(ER+,Luminal A) were induced by paclitaxel(PTX) and epirubicin(EPI) for more than 6 months,with an incremental dose,respectively.The expression and methylation status of ER-α in MCF-7 cells were detected before and after drug treatment.miRNAs with consistent expression changes in MCF-7 cells after two drugs' treatment were screened by microarray,and verified by quantitative PCR (qPCR).Targets of the most significantly down-regulated miRNA were analyzed by bioinformatics.miRNA inhibitor was transfected into MCF-7 cells,miRNA mimic was transfected into MCF-7/PTX and MCF-7/EPI cells,then ER-α and DNA methyltransferase 1 (DNMT1) expression were detected by Western blot,and ER-α methylation was detected by quantitative methylation-specific PCR (qMSP).Results PTX resistant MCF-7/PTX cell line and EPI resistant MCF-7/EPI cell line were established.Both drug treatments caused a decrease in ER-α protein expression and an increase in methylation levels,with up-regulation of DNMT1 and his tone deacetylase 1 (HDAC 1) expression.miRNAs with consistent expression changes in MCF-7 cells after drug treatments were screened and verified by qPCR,the most significant down-regulation among which was miR-148b.Bioinformatics analysis,and further confirmed by luciferase reporter gene assay (Luciferas) that DNMT1 was a direct target of miR-148b.miR-148b inhibitor induced decreased expression of ER-α and increased methylation level in MCF-7 cells,accompanied by increased expression of DNMT1;whereas miR-148b mimic caused an increased expression of ER-α and decreased methylation level in MCF-7/PTX and MCF-7/EPI cells,with a decreased expression of DNMT1.Conclusion Chemotherapeutic drugs (represented by PTX and EPI) induce aberrant miRNA expression in breast cancer MCF-7 cells,and down-regulate miR-148b further to attenuate the inhibition of DNMT1 expression,which promote,hypermethylation and down-regulation of ER-α.