Association of miR-34a with adriamycin resistance in human breast cancer MCF-7 cell line

Objective To explore the effect of miR-34a on the resistance of human breast cancer cell line MCF-7 to adriamycin( Adr) and its potential molecular mechanism. Methods An Adr-resistant subline( MCF-7 / Adr) was developed by exposing human breast cancer parental cell( MCF-7) to gradually increasing concentrations of Adr in vitro. MicroRNAs microarray and RT-qPCR were conducted to analyze the differentially expressed miRNAs in MCF-7 / Adr compared with its parental MCF-7 cells. The potential target gene of miR-34a was predicted by online bioinformatic software. Both the MiR-34a mimic and inhibitor were transfected into MCF-7 / Adr and MCF-7 cells,respectively,and the effects of the changes of miR-34a expression levels on the drug resistance were observed in the transfected cells by MTT and RT-qPCR assays. The level of Notch1 protein was determined by western blot. Results MCF-7 / Adr subline was successfully established. Compared to MCF-7,there were 156 differentially-expressed miRNAs in MCF-7 / Adr cell,among which miR-34a showed significantly low expression( t = 11. 597,P = 0. 000). The expression level of miR-34a in miR-34a mimictransfected MCF-7 / Adr elevated compared with negative control,and the sensitivity of the cells to Adr increased( t = 8. 013,P = 0. 001 and t = 18. 160,P = 0. 000),while the expression level of miR-34a reduced in miR-34a inhibitor-transfected MCF-7 and the sensitivity of the cells to Adr decreased( t = 9. 979,P = 0. 000 and t = 4. 130,P = 0. 009). Bioinformatics prediction indicated Notch1 gene should be the specific target gene of miR-34a. Western blot analysis showed that the level of Notch1 protein decreased in miR-34a mimic-transfected MCF-7 / Adr( F = 64. 949,P = 0. 000) and increased in miR-34a inhibitor-transfected MCF-7( F = 10. 938,P = 0. 010),compared with blank control and negative control. Conclusion MCF-7 / Adr resistant subline shows different miRNA expression profile as compared with its parental cell line. miR-34a is involved in the resistance formation of breast cancer cells to Adr and Notch1 may be one of the target genes in regulation of miR-34a.