STAT3 and cancer: Signal transducer and activator of transcription-3 is part of a family of cytokine and growth factor-activated transcription factors, which includes STAT1, STAT2, STAT4, STAT5a/b, and STAT6, which are signaling proteins, targets of phosphorylation by Jak and receptor tyrosine kinases (RTKs), as well as transcription factors whose effects on gene expression profoundly impact the immune response, the outcome of viral infections, embryonic development, and cancer biology (39–43).