Effects of ATRA, IFNα, G-CSF and the combination of G-CSF and ATRA on Stat 1α protein and Stat 1 mRNA in freshly isolated APL cells and the two myelogenous leukemia cell lines U937 and HL-60. (A) Leukemic cells obtained from the BM of 4 different APL patients, U937 and HL-60 cells were seeded at a concentration of 4 × 105/mL and treated for 4 days as indicated. Cells were obtained, lysed, and the cell extracts (10 μg of protein/lane) subjected to Western blot analysis, using antibodies specific for Stat 1α. (B) Freshly isolated leukemic cells (4 × 105/mL) from three APL patients were treated for 4 days, as indicated. Total RNA was isolated and subjected (20 μg/lane) to Northern blot analysis. Filters were sequentially hybridized with cDNA probes coding for Stat 1α and β-actin. For all the experiments shown, the following stimuli were used: ATRA (10−6 mol/L), G-CSF (10 ng/mL), the combination between ATRA and G-CSF, and IFNα (1,000 U/mL).
