SMAD4 and breast carcinoma: Xue et al. showed that FOXM1 promotes breast cancer metastases by activation of the TGF-β pathway through interaction with SMAD3 (this prevented E3 ubiquitin-protein ligase transcriptional intermediary factor 1 γ [TIF1 γ] binding to SMAD3 and protected SMAD4 from ubiquitination) that leads to stabilization of the SMAD3/SMAD4 complex [39].