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AIM:TO explore the reversal effect of mifepristone onmultidrug resistance(MDR)in drug-resistant human gastriccancer cell line SGC7901/VCR and its mechanisms.METHODS:Expression of multidrug resistance-associatedprotein(MRP)was detected using reverse transcription-polymerase chain reaction(RT-PCR).Flow cytometry wasused to assay the expression of P-glycoprotein(P-gp),Bcl-2,Bax,and the mean fluorescent intensity of intracellularrhodamine 123 in the cells.Meanwhile,the protein levelsof Bcl-2 and Bax were also detected by Western blottinganalysis.The sensitivity of cells to the anticancer agent,vincrimycin(VCR),and the intracellular [~3H]VCR accumulationwere determined by tetrazolium blue(MTT)assay and aliquid scintillation counter,respectively.RESULTS:Expression of MRP and P-gp in SGC7901/VCRcells was 6.04-and 8.37-fold higher as compared with itsparental SGC7901 cells,respectively.After treatment with1,5,10,and 20 μmol/L mifepristone,SGC7901/VCR cellsshowed a 1.34-,2.29-,3.11-,and 3.71-fold increase in theaccumulation of intracellular VCR,a known substrate of MRP,and a 1.03-,2.04-,3.08-,and 3.68-fold increase in the retentionof rhodamine 123,an indicator of P-gp function,respectively.MTT assay revealed that the resistance of SGC7901/VCRcells to VCR was 11.96-fold higher than that of its parentalcells.The chemosensitivity of SGC7901/VCR cells to VCRwas enhanced by 1.02-,7.19-,12.84-,and 21.17-fold aftertreatment with mifepristone at above-mentioned dose.After96 h of incubation with mifepristone 10μmol/L,a concentrationclose to plasma concentrations achievable in human,theexpression of Bcl-2 protein was decreased to(9.21±0.65)%from(25.32±1.44)%,whereas the expression of Bax proteinwas increased to(19.69±1.13)% from(1.24±0.78)%(P<0.01).Additionally,the effects of mifepristone on theexpression of Bcl-2 and Bax proteins in SGC7901/VCR cellswere further demonstrated by Western blotting analysis.CONCLUSION:Mifepristone has potent reversal effect onMDR in SGC7901/VCR via inhibiting the function of MRP andP-gp,modulating the expression of Bcl-2 and Bax proteins,and enhancing the sensitivity to anticancer agent VCR.
AIM: TO explore the reversal effect of mifepristone on multidrug resistance (MDR) in drug-resistant human gastric cancer cell line SGC7901 / VCR and its mechanisms. METHODS: Expression of multidrug resistance-associated protein (MRP) was detected using reverse transcription- polymerase chain reaction RT-PCR). Flow cytometry was used to assay the expression of P-glycoprotein (P-gp), Bcl-2, Bax, and the mean fluorescent intensity of intracellular rhodamine 123 in the cells. were also detected by Western blotting analysis of the sensitivity of cells to the anticancer agent, vincrimycin (VCR), and the intracellular [~ 3H] VCR accumulation determined by tetrazolium blue (MTT) assay and aliquid scintillation counter, respectively .RESULTS: Expression of MRP and P-gp in SGC7901 / VCR cells were 6.04-and 8.37-fold higher compared to its parental SGC7901 cells, respectively. After treatment with 1, 5, 10 and 20 μmol / L mifepristone, SGC7901 / VCR cellsshowed a 1.34-, 2.29- , 3.11-, and 3.71-f old increase in the accumulation of intracellular VCR, a known substrate of MRP, and a 1.03-, 2.04-, 3.08-, and 3.68-fold increase in the retention of rhodamine 123, an indicator of P-gp function, respectively. MTT assay revealed that the resistance of SGC7901 / VCR cells to VCR was 11.96-fold higher than that of its parental cells. The chemosensitivity of SGC7901 / VCR cells to VCR was enhanced by 1.02-, 7.19-, 12.84-, and 21.17- fold aftertreatment with mifepristone at above-mentioned dose. After 96 h incubation with mifepristone 10 μmol / L, a concentration of clonal plasma concentrations achievable in human, the expression of Bcl-2 protein was decreased to (9.21 ± 0.65)% from (25.32 ± 1.44)%, Additionally, the effects of mifepristone on theexpression of Bcl-2 and Bax proteins in SGC7901 / VCR cellswere further demonstrated by Western blotting analysis. CONCLUSION: Mifepristone has potent reversal effect on MDR in SGC7901 / VCR via inhibiting the function of MRP and P-gp, modulating the expression of Bcl-2 and Bax proteins, and enhancing the sensitivity to anticancer agent VCR.