Down-regulation of MLL PTD fusion transcript is associated with induction of MLL WT and reduced AML-CFUs. (A) Antisense inhibition of expression of the MLL PTD with the exon 12 to exon 5 self-fusion in primary MLL^PTD/WT AML blasts. Cells were treated as described in “Materials and methods” and using 10 μg/mL phosphothiorated ODNs. QRT-PCR was performed in duplicate to determine the MLL WT/MLL PTD transcript ratio after treatment in vitro with media only or ODNs. Data are presented as the percentage of total MLL transcript present in the sample. (B) Inhibition of AML blast-colony-forming unit (CFU) formation using antisense ODNs (10 μg/mL) directed against the MLL PTD of exons 5 through 12. Cells were treated as described in “Materials and methods” and plated in media-supplemented methylcellulose for colony formation. The number of colonies arising in the media-only controls represents maximal growth (100%). Results are presented as the percentage of growth relative to media-only control growth ± SD and are representative of 3 separate experiments.