TGFB1 and breast cancer: It is widely accepted that TGF-β is a potent inducer of SKI (and SnoN) degradation [22-29], and we recently demonstrated that in breast cancer cells, TGF-β suppresses the ability of SKI to inhibit tumor metastasis by inducing its degradation via the ubiquitin-proteasome pathway, whereby TGF-β induces the E3 ubiquitin-ligase Arkadia to mediate SKI degradation in a SMAD-dependent manner [22].