Studies from our group demonstrated that overexpression of SIX1 in the breast cancer cell line MCF-7 converted transforming growth factor-ß (TGF-ß) signaling from tumor suppressive to tumor-promotional (Micalizzi et al., 2010), and this modification of TGF-ß signaling additionally promoted EMT and enhanced metastasis in both experimental and spontaneous mouse models (Micalizzi et al., 2009). This evidence concerns the gene SIX1 and breast cancer.