Pharicin B overcomes ATRA resistance in some NB4-derived and ATRA-resistant cell lines. (A) Percentages of growth inhibition, CD11b expression, and NBT reduction for ATRA-resistant cells NB4-MR2, NB4-LR1, and NB4-LR2 treated with 2μM pharicin B, 0.1μM ATRA, or both for 3 days. (B) Cells were treated as in (A), but for 48 hours, and RAR-α/PML-RAR-α protein was detected by antibody of RAR-α. β-actin was used as the internal control. Each experiment was repeated at least 3 times. The number on the bottom indicates signal intensity of RAR-α protein against β-actin.