Signal Transducer and Activator of Transcription 3 (Stat3) is a transcription factor that mediates the nuclear action of many different cytokines and growth factors. It plays roles in cell growth and apoptosis. Stat3 also participates in cellular transformation and tumorigenesis. The aberrant activation of Stat3 in tumor cells has been considered as a drug target. Stat3 is activated by tyrosine phosphorylation in response to a wide range of cytokines, growth factors, and hormones. Tyrosine phosphorylation triggers dimerization and nuclear translocation of the protein. Stat3 mediates the expression of its target genes that are involved in a diverse array of biological processes such as oncogenesis, cell growth, and differentiation. 
Signosis has developed a plate-based array for profiling 20+ Stat3-regulated genes. By using this assay, researchers are able to compare gene expression in up to three samples on a single microtiter plate.