RESUMEN
<p><b>OBJECTIVE</b>To screen effective sequences of small interfering RNA targeting MDR1 gene in human gastric cancer SGC7901/VCR cells.</p><p><b>METHODS</b>Four siRNAs (MDR1si326, MDR1si1513, MDR1si2631 and MDR1si3071) targeting MDR1 gene were designed and synthesized by in vitro transcription. The siRNA duplexes were used to transfect into the human gastric cancer SGC7901/VCR cells. The expression level of MDR1 mRNA and P-gp were detected by RT-PCR and Western blotting, respectively. The accumulation of intracellular adriamycin (ADR) was examined by flow cytometry and the cell sensitivity to ADR was demonstrated by MTT.</p><p><b>RESULTS</b>The SGC7901/VCR cells treated with 4 siRNAs led to reversal effect on multidrug resistance to different extents. Among the SGC7901/VCR cells treated by siRNAs for 48 h, the expression level of MDR1 mRNA in cells of MDR1si326 or MDR1si2631 group (0.42 +/- 0.07 or 0.49 +/- 0.02) was more decreased than that in cells of MDR1si1513 or MDR1si3071 group (P < 0.05). The accumulation of ADR in cells of MDR1si326 group was the most; in cells of MDR1si2631 group, more; in cells of MDR1si3071 group, lower and in cells of MDR1si1513 group, the lowest (P < 0.05). The relative reversal efficiency of cells of MDR1si2631 group to ADR was the highest and in cells of MDR1si326 group, higher (P < 0.05). There was no significant difference in the relative reversal efficiency between the cells of MDR1si1513 and MDR1si3071 groups (P > 0.05). The expression level of P-gp in cells of MDR1si326 group was the lowest among the SGC7901/VCR cells treated by siRNAs for 72 h.</p><p><b>CONCLUSION</b>The MDR1si326 with most, MDR1si2631 with more, MDR1si3071 with less and MDR1si1513 with least reversal effects on MDR1 gene mediated multidrug resistance were found in the human gastric cancer SGC7901/VCR cells.</p>