STAT3 and breast cancer: (2) Signal transducer and activator of transcription 3 (Stat3). Evidence indicates that the IL-6/JAK/Stat3 pathway plays a critical role in the pathogenesis of breast cancer, and that dysregulated Stat3 activation promotes breast tumor progression due to overexpression of a plethora of target genes involved in cell survival, angiogenesis, and EMT [53].