A novel approach for the generation of genetically modified mammary epithelial cell cultures yields new insights into TGFβ signaling in the mammary gland

Table 1 Receptor-activated Smad dependency of different biological responses to TGFβ in mammary epithelial cells

Biological response to TGFβ	Potential role in tumorigenesis	Receptor-activated Smad requirement
Growth inhibition	Tumor suppression	Smad3
Apoptosis	Tumor suppression	Smad3; Smad2 opposes
Migration and invasion	Pro-progression	Smad2 or Smad3; a threshold level of receptor-activated Smad must be exceeded
Epithelial-to-mesenchymal transition	Pro-progression	Smad3; Smad2 opposes basally
Induction of metalloproteinases (MMP-9)	Pro-progression	Smad2 or Smad3

Smad, Sma and MAD (mothers against decapentaplegic)-related protein; TGFβ, transforming growth factor beta.

ISSN: 1465-542X