Changes in the sensitivity of K562/ADM cells to DNR after oligonucleotide treatment (5 μmol/L). Leukemic blast colony assays were performed in untreated (▪), random- (□), MDR1-S– (○), and MDR1-AS–treated cells (•). The results are expressed as the percentage of DNR treated colonies compared with the DNR untreated control, and represent the mean ± the SD of colony numbers of three dishes.