SMAD3 and breast cancer: Previous studies show that BMP7 induces Smad5 signaling to antagonize TGF-β-induced Smad3 nuclear accumulation and block the transcriptional up-regulation of the Smad3 target CAGA box promoter activity in mesangial cells (Wang and Hirschberg, 2004b), but in breast cancer cells, BMP7 appears inhibiting TGF-β-induced Smad3 target CAGA box promoter activity (Buijs et al., 2007a).