Effects of mcl-1 ASOs on MCL-1 protein expression and cell viability in STI571-sensitive and STI571-resistant K562 cells. STI571-sensitive K562 cells (A-D) and STI571-resistant K562 cells (E-H) were transfected with an mcl-1 ASO at 250 nM (antisense) or a scramble control or were left untransfected (control). After 24 hours, cells were subjected to Western blot analysis (A-B,E-F), trypan blue exclusion test (C,G), and evaluation of numbers (%) of apoptotic cells (D,H). Western blot analysis was performed using an MCL-1 antibody; BAK or β-actin served as loading control. Representative Western blot experiments for STI571-sensitive K562 cells (A) and STI571-resistant K562 cells (E) as well as a densitometric evaluation of Western blot data (B,F) are shown. Results represent the mean ± SD from 3 independent experiments; ^*P < .05.