STAT3 is a member of the signal transducers and activators of transcription (STAT) family of proteins that carry out a dual function: signal transduction and activation of transcription. STAT3 is widely expressed and becomes activated through phosphorylation on tyrosine as a DNA binding protein in response to a variety of stimuli such as EGF, IL-6, PDGF, IL-2 and G-CSF. This phosphoprotein forms homodimers as well as heterodimers with other members of the STAT family and translocate to the nucleus in order to modulate the transcription of various genes.