STAT3 protein plays an important role in development, immune system and inflammation. When activated, STAT3 translocates from cytoplasm to nucleus, binds to the STAT3 responsive element and regulates the expression of genes, involving in cell growth, division, transformation and apoptosis. Dysfunction of STAT3 is closely associated with many diseases, such as cancers. Constitutively activated forms of STAT3 have been detected in many cancer cell lines and primary tumors. Signosis has developed STAT3 filter plate assay for monitoring DNA binding activity of STAT3, which can analyze multiple samples simultaneously.