The JAK/STAT Pathway

Cellular responses to dozens of cytokines and growth factors are mediated by the evolutionarily conserved Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway (Fig. 1).These responses include proliferation, differentiation, migration, apoptosis, and cell survival, depending on the signal, tissue, and cellular context.JAK/STATsignaling is essential for numerous developmental and homeostatic processes, including hematopoiesis, immune cell development, stem cell maintenance, organismal growth, and mammary gland development (Ghoreschi et al. 2009).Janus kinases (JAKs) were identified through sequence comparisons as a unique class of tyrosine kinases that contain both a catalytic domain and a second kinase-like IL-6 gp130