siRNAs silence expression of mdr1 gene and its role in reversing drug-resistance in K562/ADM cells / 中国癌症杂志

ABSTRACT

Background and purpose:Drug-resistance is the main obstacle in terms of efficacy of chemotherapy for leukemia, RNA interference(RNAi) strategy possesses the characteristics of specilization, high-efficiency and low-toxicity, and can effectively and specifically inhibit the overexpression of given gene. This study was designed to investigate the effect of small interfering RNA (siRNA) on expression of mdr1 gene and drug-resistance in multidrug-resistant human leukemia K562/ADM cell.Methods:Human multidrug-resistant leukemia cell line K562/ADM over-expressing mdr1 gene was used as the target cells, Two siRNAs (si-mdr1-1 and si-mdr1-2) targeted mdr1 gene were chemically synthesized and transfected into K562/ADM cells. Expression of mdr1 mRNA was determined by RT-PCR, P-glycoprotein (P-gp) expression was measured using flow cytometry (FCM), and the sensitivity of K562/ADM cells to adriamycin was assessed with a MTT colorimetric assay.Results:Two siRNAs (si-mdr1-1 and si-mdr1-2) specially designed in this study could markedly down-regulate the expression of mdr1 mRNA and its product P-gp in K562/ADM cells. After cells transfected with si-mdr1-1 or si-mdr1-2 for 24h and 48h, the inhibition of mdr1 mRNA expression in the cells for si-mdr1-1 was 55.5% and 22.5%; and for si-mdr1-2, 16.0% and 57.6%, respectively. Treated with siRNA for 72h, the expression intensity of P-gp in the two transfected cell lines decreased 74% and 85%, respectively. Both si-mdr1-1 and si-mdr1-2 significantly enhanced the sensitivity of K562/ADM cells to adriamycin and reversed their drug-resistance, the reversal efficiency was 2.52-folds and 1.96-folds, respectively.Conclusions:The siRNA could effectively and specifically silence the expression of mdr1 gene and overcome the drug-resistance mediated by P-gp in K562/ADM cells.