Reversal of multi-drug resistance by vector-based-shRNA-mdr1 in vitro and in vivo.

In order to investigate the effects of vector-based hairpin small interference RNA (shRNA) on the reversal of multi-drug resistance (mdr) of A2780/Taxol cells, a novel vector pEGFP-H1/mdr1 containing mdr1-shRNA targeting at position 2943-2963 of mdr1 was designed and synthesized. Subsequently, A2780/Taxol cells were transfected with pEGFP-H1/mdr1, and the expression of mdr1 mRNA and P-gp was detected by using RT-PCR and Western blot respectively. MTT was used to measure the 50% inhibition concentration (IC(50)) of Taxol to A2780/Taxol cells. The results showed that at the 24th and 48th h after transfection, the expression of mdr1 mRNA was decreased to (52.1+/-1.0)% and (0.01+/-1.7)%, and that of P-gp decreased to (88.3+/-2.1)% and 0%, respectively. At the 48th h after transfection, the relative reversal rate of A2780/Taxol cells to Taxol was 69.54%. In vivo, the nude mice xenografts were injected with pEGFP-H1/mdr1, and then administrated Taxol. The tumor volume in pEGFP-H1/mdr1-transfected group was significantly reduced as compared with that in blank control group or pEGFP-H1-transfected group (807.20+/-103.16 vs 1563.78+/-210.54 or 1480.78+/-241.24 mm(3), both P<0.01). These results suggested that transfection of pEGFP-H1/mdr1 could efficiently down-regulate the expression of mdr1 mRNA and P-gp in A2780/Taxol cells, and effectively restore the sensitivity of A2780/Taxol cells to Taxol both in vitro and in vivo.