Abstract: OBJECTIVE:To investigate the use of siRNA to silence the breast cancer resistance protein (BCRP/ABCG2) on overcoming multidrug resistance in breast cancer cells. METHODS:The morphologic,particle size,surface potential of magnetic nanoparticles (polyMAG) were characterized by transmission electron microscopy and by zeta potential analyzer,and the binding capacity of siRNA and polyMAG were investigated by gel retardation assay. We used polyMAG as a carrier to deliver several concentrations of siRNA (5,10,20,50,100 nmol/L) effectively into MCF-7/ADR cells. Quantitative real-time PCR (qPCR) and Western blotting were used to detect ABCG2 levels. CCK-8 and Calcein-AM/PI were stained and used to detect cell proliferation. RESULTS:The average size and zeta potentials of polyMAG was about 100 nm and 29.6 mv. Gel retardation assay confirmed that siRNA was well packaged into polyMAG under polyMAG/siRNA ratios 1:1 and 1:2. Cell viability of MCF-7/ADR was reduced while siRNA concentrations changed from 20 nmmol/L to 100 nmmol/L,compared with non-siRNA transfection (P < 0.05). Expression of ABCG2 mRNA was significantly down-regulated in the 20 nmol/L polyMAG-siRNA transfected group,which was about 1/8 of the un-transfected group (P < 0.05),and apoptotic cells were significantly increased compared with other groups. 50 nmol/L polyMAG-siRNA significantly interfered with the expression of ABCG2 protein (P < 0.05). CONCLUSION:polyMAG-siRNA effectively perturbed the ABCG2 expression and enhanced DOX susceptibility of MCF-7/ADR to overcome multidrug resistance in breast cancer cells.

Key words: magnetic nanoparticles, siRNA, breast cancer resistance protein, multidrug resistance