B-cell chronic lymphocytic leukemia (CLL) is the most common adult leukemia in the Western hemisphere. Although several chromosomal and molecular abnormalities have been identified in CLL cells in recent years, the pathogenesis of CLL is still poorly understood. Signal transducer and activator of transcription 3 (STAT3) plays a major role in cellular physiology. Upon exposure to cytokines or growth factors, STAT3 is tyrosine-phosphorylated, migrates to the nucleus, and binds to DNA. Constitutive phosphorylation of STAT3 on tyrosine 705 residues has been found in several solid tumors and hematologic malignancies. Remarkably, CLL is the only disease in which STAT3 is constitutively phosphorylated (p) on serine rather than tyrosine residues (
Disclosures: No relevant conflicts of interest to declare.