RESUMO
OBJECTIVE@#To investigate the suppression of MDR1 and P-glycoprotein induced by small interfering RNA and the restoration of sensitivity to chemotherapeutic drugs in multidrug-resistant hepatocellular carcinoma cell line Bel7402/5-Fu.@*METHODS@#MDR1j targeted small interfering RNA duplexes were introduced into multidrug-resistant hepatocellular carcinoma cell line Bel7402/5-Fu. The suppression of MDR1 and its gene product P-glycoprotein was examined by RT-PCR and Western blot. MTT assay was performed to measure the reverse effect of small interfering RNA based on the results of IC50. Cell apoptosis was assessed by flow cytometry after various cell lines were treated with chemotherapeutic drugs.@*RESULTS@#The overexpression of MDR1 and P-glycoprotein was suppressed efficiently by the introduction of small interfering RNA, which caused sequence-specific gene silence. The level of MDR1 in the transfected Bel7402/5-Fu cells reduced to 22.55% and P-glycoprotein to 25.49% compared with those of the controls. The apoptosis rate of Bel7402/5-Fu cells increased significantly in the siRNA group during the chemotherapy (P<0.01). Their resistance to 5-Fu was reversed by 14.88 folds, which indicated the restoration of sensitivity to drugs.@*CONCLUSION@#Small interfering RNA can inhibit MDR1 expression effective and reverse the multidrug resistance mediated by P-glycoprotein.