Viability of L2-RYC cells in each concentration was calculated Selisistat price as ODtreated/ODuntreated × 100%. The half maximal inhibitory concentration (IC50) was accounted to compare the drug sensitivity among each group. Statistical analyses All data were shown as mean ± standard deviation (SD). Statistical analyses were performed using SPSS 15.0 software package (SPSS, Inc, Chicago, IL). Mann-Whitney U test was performed to compare results among experimental groups. P < 0.05 was considered

as statistically significant. Results Construction and silencing efficiency of pSEB-siMDR1 plasmids expressing siRNAs against MDR1 We subcloned four pairs of siRNA oligonucleotide cassettes that target rat MDR1 coding region using the previously developed pSOS system [28]. After inserting the cassettes into the pSEB-HUS vector, we were able to amplify and confirm an approximately 300 bp of PCR product in the four recombinant pSEB-siMDR1 plasmids using U6 promoter primer and antisense oligonucleotide of siRNA cassettes (Figure 1A). A NotI restriction enzyme site was removed when siRNA oligonucleotide cassettes were inserted into multi cloning sites of pSEB-HUS vector. When we used NotI to digest Selleckchem AUY-922 pSEB-siMDR1

plasmids, no about 1300 bp DNA fragment was seen in corrected recombinants compared with pSEB-HUS vector which could be cut out to be about 1300 bp DNA fragment and another large DNA fragment (Figure 1B). Next, we tested the silencing efficiency of different Diflunisal siRNA target sites and found that three of the four pSEB-siMDR1 plasmids transfection decreased the mRNA level of MDR1 in L2-RYC cells. The highest

silencing efficiency was observed in the pooled plasmids group (Figure 1C). Therefore, for the following experiment, we chose to use the pooled plasmids to transfect cells. Figure 1 Construction of recombined plasmids containing siMDR1 and inhibition of endogenous MDR1 gene expression. (A) Identification of recombinant pSEB-siMDR1 plasmids by PCR amplification, About 300 bp of DNA fragment was PCR amplified from pSEB-siMDR1 plasmid template by U6 promoter primer and antisense of siRNA sequence. (1. negative control; 2. PCR product from pSEB-siMDR1-1 plasmid; 3. PCR product from pSEB-siMDR1-2 plasmid; 4. PCR product from pSEB-siMDR1-3 plasmid; 5. PCR product from pSEB-siMDR1-4 plasmid; 6. DNA Ladder, 600 bp, 500 bp, 400 bp, 300 bp, 200 bp, 100 bp). (B) Identification of recombinant pSEB-siMDR1 plasmids by NotI restriction enzyme digestion, No small DNA fragment was digested from corrected recombinant pSEB-siMDR1 plasmids by NotI enzyme compared with pSEB-HUS vehicle vector (7. NotIenzyme-digested pSEB-HUS vehicle vecter; 8. NotIenzyme-digested pSEB-siMDR1-1 plasmid; 9. NotIenzyme-digested pSEB-siMDR1-2 plasmid; 10. NotIenzyme-digested pSEB-siMDR1-3 plasmid; 11. NotIenzyme-digested pSEB-siMDR1-4 plasmid;12.