Effect of STI571 and ATRA on the steady-state levels of the transcripts coding for CD11b; the components of the NADPH-oxidase complex; the transcription factors cEBPε, IRF-1, and STAT1; as well as cEBPε and STAT1 proteins.
NB4 cells were seeded at an initial concentration of 2 × 105/mL and treated for 4 days (A and C) or the indicated amount of time (B) with vehicle alone, STI571 (5 × 10−6 M), ATRA (10−7 M), and the combination of the 2 compounds. In (A) and (B), the steady-state levels of the indicated transcripts were measured by Northern blot analysis, using total RNA (20 μg/lane) and 32P-labeled specific cDNA probes. In (C), cEBPε and STAT1 protein levels were determined by Western blot analysis (●, intact form of STAT1; *, degradation product of the protein). Determination of NBT-reducing activity in parallel cultures at the time of RNA harvesting gave the following results in ΔO.D. at 540 nm: control = 0.21; STI571 = 0.21; ATRA = 0.41; STI571 + ATRA = 0.92.
