Smad signaling antagonizes STAT5-mediated gene transcription and mammary epithelial cell differentiation.

Both the transforming growth factor-beta (TGFbeta)/Smad and the prolactin/JAK/STAT pathway are critical to the proper development, maintenance, and function of the mammary epithelial tissue. Interestingly, opposing physiological effects between these two signaling pathways are prominent in the regulation of mammary gland development. However, the exact nature of the biological network existing between the Smad and STAT signal transduction pathways has remained elusive.