Dr. Jekyll and Mr. Hyde: a paradoxical oncogenic and tumor suppressive role of signal transducer and activator of transcription 3 in liver cancer.

摘要

Unrestrained activation of the signal transducer and activator of transcription (Stat) signaling cascade frequently occurs in a wide variety of tumor types.1"3 In this pathway, binding of extracellular ligands such as cytokines, hormones, and growth factors to their specific receptors leads to the activation of Janus tyrosine kinases (Jakl, Jak2, Jak3, and Tyk2). ' These tyrosine kinases are able to phosphorylate a single tyrosine residue of each Stat protein. Similarly, non-receptor tyrosine kinase such as Abelson murine leukemia viral oncogene homolog (c-ABL) and Schmidt-Ruppin A-2 viral oncogene homolog (c-SRC) can directly phosphorylate Stat proteins in the absence of ligand-induced receptor signaling.