Constitutive and non-IL-6–inducible Stat3 phosphorylation patterns are observed in 25% of the investigated patients with AML.

AML cells and HepG2 cells were plated in 12-well culture plates, either unstimulated or stimulated with 10 ng/mL IL-6 for 15 minutes (AML) or for 5 to 60 minutes (HepG2), and equal amounts of total cell lysates were subjected to SDS–PAGE followed by Western blot analysis. Phosphorylated Stat3 was visualized using phospho-specific antibodies recognizing Tyr705- and Ser727-phosphorylated Stat3. As a control, equal amounts of total cell lysates were Western blotted using antibodies against Stat3 (K-15).