Reversal of adriamycin resistance in human mammary cancer cells by small interfering RNA of MDR1 and MDR3 genes.

The purpose of this paper is to investigate the reversal effect of small interfering RNA (siRNA) targeting MDR1 and MDR3 genes on the resistance of MCF-7/ADR cells to adriamycin. siRNA plasmid vector targeting MDR1 and MDR3 genes was transfected into MCF-7/ADR cells, and then was stained with Annexin-V FITC (fluorescein isothiocyanate conjugated) to detect the early stage cell apoptosis by flow cytometry (FCM). 50% inhibition concentration (IC50) of adriamycin for MCF-7/ADR cells was determined by MTT method. MDR1 and MDR3 mRNA was assessed by RT-PCR. Treatment of MCF-7/ADR cells with the two kinds of siRNAs resulted in a reversal of adriamycin resistance of MDR to different extents. 1) The apoptosis efficiency of MDR1 and MDR3 siRNA vector after transfection was (18.21+/-1.65) % and (9.07+/-2.16) % respectively (P<0.05), and there was significant differences in the apoptosis efficiency between p Suppressor Neo vector and the MDR1 siRNA or MDR3 siRNA vector (P<0.01); 2) The reversal effect of MDR1 siRNA is higher than that of MDR3 siRNA (P<0.05); 3) The expression of MDRI and MDR3 mRNA can be restrained by p Suppressor Neo MDR1 and MDR3 siRNA respectively, and the reduction in the mRNA level was in a time-dependent manner (P<0.01). MDR1 and MDR3 gene silencing can enhance intracellular adriamycin accumulation in MCF-7/ADR cells, improve sensitivity of MCF-7/ADR cells to adriamycin, and induce cell apoptosis. The reversal effect of adriamycin resistance by siRNA of MDR1 was more effective than that of MDR3.