Objective: To investigate the multidrug resistance (MDR) reversal activity of schisandrin B (SchB) in transfected human breast cancer cell line MCF-7/MDR1.
Methods: Human breast cancer cells of the line MCF-7 were cultured and transfected with mdr1 gene so as to establish a P-glycoprotein (P-gp) stable-expressing cell line MCF-7/MDR1. The expression of P-gp in the MCF-7/mdr1 cells was assayed by flow cytometry using fluorescent antibody. MCF-7 cells transfected with blank plasmid MCF-7/neo was used as controls. Adriamycin (ADR), verapamil (VER), pacilitaxel (taxol), and homoharringtonine (HHT) were added into the culture fluid of the MCF-7/mdr1 cells and MTT method was used to detect the IC(50) of these drugs. The culture fluid of the MCF-7/MDR1 cells was added with SchB of the concentrations of 2.5, 12.5, 25, and 50 micromol/L and then added with ADR1 cells, MTT method was used to calculate the reversal effect (RF) of SchB on the MDR phenotype of the MCF-7/mdr1 cells. MTT method was used to calculate the RF. Another culture fluid of MCF-7/mdr1 cells was added with 25 micromol/L SchB and then with ADR, vincristine (VCR), pacilitaxel, and HHT with that added with 10 micromol/L VER as control. After treatment with SchB the MF7/mgr1 cells were co-incubated with 5 micromol/L rhodamine (Rh)-123, then flow cytometry was used to detect the accumulation of Rh-123 within the cells. After treatment with 25 micromol/L SchB for 0, 0.5, 1, 6, 24, 48, and 72 hours flow cytometry was used to detect the P-gp expression in the MF7/mgr1 cells.
Results: The transfected MCF-7/MDR1 cells overexpressed P-gp and exhibited resistance to multiple drugs, including ADR, VCR, pacilitaxel and HHT. SchB (25 micromol/L) significantly enhanced the sensitivity of the MCF-7/MDR1 cells to above mentioned chemotherapeutic agents, with a reversal factors of 6.03 to 23.94 times. The effect of SchB (25 micromol/L) on Rh-123 accumulation in MDR cells was equivalent to that of 10 micromol/L VER, however no significant difference was found in the effect of SchB (25 micromol/L) on the P-gp expression in the MCF-7/MDR1 cells.
Conclusion: SchB is able to restore the drug sensitivity in the transfected MCF7/MDR1 cells, with a possible mechanism of increasing the drug influx via inhibiting the P-gp function.