SMAD2 and breast carcinoma: Collectively, our data presented here suggest that overactive Activin A signaling may promote tumorigenesis, migration and lung metastasis of breast cancer, at least in part, by inducing directly or indirectly IL13Rα2 expression in a Smad2-depended manner (Figure 7), without excluding the possibility that additional downstream effector genes could also be involved in this process.