SignalStain^® Phospho-Stat IHC Sampler Kit #8113

Stat proteins serve as transcription factors in growth and survival pathways stimulated by growth factor and cytokine activation of receptor proteins. Receptor activation promotes tyrosine phosphorylation of Stat proteins, resulting in Stat dimerization and translocation to the nucleus where they regulate expression of numerous proteins that control cell growth, survival, differentiation and pathogen resistance (1). Stat1 is essential in IFN-α and IFN-γ stimulated pathways and is abnormally activated in many tumors (2,3). Both Stat1α (91 kDa) and Stat1β (84 kDa) isoforms are activated by IFN-α but only Stat1α responds to IFN-γ. Phosphorylation of Stat1 at Tyr701 induces Stat1 dimerization, nuclear translocation and DNA binding (4). Transcription factor Stat3 possesses oncogenic potential and anti-apoptotic activities; a number of human tumors display constitutively activated Stat3 (5,6). Activation of Stat3 follows phosphorylation at Tyr705, resulting in dimerization, nuclear translocation and DNA binding (7). Expression of Stat3α (86 kDa) and Stat3β (79 kDa) isoforms correlates with cell type, ligand and cell maturation stage (8). Phosphorylation of Stat5a at Tyr694 is essential for transcription factor activation (9). Stat5 is activated by interleukins and other cytokines (i.e. CSF1); presence of phosphorylated Stat5 is in some IL-3-treated cells suggests a role in angiogenesis and cell motility (10). Altered Stat5 expression and activity is associated with abnormal cell proliferation and apoptosis in some forms of leukemia (11).