STAT3 and leukemia: In this study we demonstrate that glucosamine suppresses the phosphorylation of STAT3 (Tyr705), thereby inhibiting its DNA binding and transcriptional activities, and retards the proliferation of DU145 and Hela cells (Fig. 6B) and the leukemia K562 cells (our unpublished data and ref. 10), all of which express constitutively active phosphorylated STAT3.