Table 1. The Role of STAT Isoform and Their Deficiency.

Isoform of STATs	Activators	Function	Deficiency
STAT1(antiapoptotic)	Interferon (IFN) stimulation and supports immune	Function partly by controlling the growth and apoptosis of immune cells 4	Leads to tumor
STAT2	IFN-α and IFN-β	Promotes STAT3 activation 10	Up regulation of interleukin-6 (IL-6)
STAT3	These genes include those that encode p21WAF1/CIP2, cyclin D1, MYC, BCL-XL, BCL-2, vascular endothelial growth factor (VEGF), matrix metalloproteinase 1 (MMP1), MMP7, and MMP9, and survivin16,17,19,19, 21,22,23	Essential for early embryonic development	That STAT3 functions are essential for IL-6-mediated antiapoptotic responses 13 STAT3 for promoting malignant transformation and progression
STAT4		Crucial mediator of IL-12 function that regulates the differentiation of TH1 cells and their inflammatory responses 5	Associated with autoimmune diseases
STAT5A		Important in mammary gland development and milk production	Defects in IL-2 receptor-α expression in T lymphocytes 12
STAT5B		Promoting cancer, including the induction of proproliferative and antiapoptotic genes	Aberrant STAT5 activation by BCR–ABL in CML
STAT6	IL-4 and IL-13