ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effectiveness of phosphorothioate multidrug resistance gene 1 (MDR1) antisense oligodeoxynucleotides (MDR1-AS) suppressing MDR1 expression in multidrug-resistant glioma cell line C6/adr.</p><p><b>METHODS</b>The glioma cell line C6/adr served as the tested model in vitro, MDR1-AS (5'-CTCCATCACCACCTC-3'), complementary to the -9- +6 sequence of first exon, was synthesized and phosphorothioate-modified. As control of sequence specificity, MDR1-S (5'-GAGGTGGTGA TGGAG-3') was used. Both antisense and sense oligodeoxynucleotides were transduced to C6/adr cells by lipofectin. The cytotoxity of MDR1-AS was tested using morphological observation and 3- (4,5-dimethylthiazol-2-yl) -2, 5-diphenyl tetrazolium bromide assay. Semi-quantitative reverse transcription polymerase chain reaction was used to monitor the expression levels of the MDR1 mRNA in the different groups. The positive rate of the MDR1 gene product P glycoprotein (P-gp) was determined by flow cytometry assessment.</p><p><b>RESULTS</b>No cytotoxicity of MDR1-AS was observed. The MDR1 mRNA expression level was decreased from 106% to about 30.44% 48 h after MDR1-AS treatment. The P-gp positive rate of MDR1-AS treated C6/adr cells decreased from 100% to 32.77%, with that of C6/adr cells considered as 100%.</p><p><b>CONCLUSIONS</b>MDR1-AS can effectively inhibit MDR1 expression in the C6/adr cell line at both the mRNA and protein level, and may be an alternative treatment of drug-resistant gliomas.</p>