Pharmacological interrogation using TGF-βRI kinase inhibitors [SB-431542 (89, 90), LY-294002 (91)], MMP inhibitor GM6001 (92), and Smad4 genetic ablation demonstrated that blockade of different parts of the TGF-β signaling pathway results in a significant reduction in breast cancer cell invasion and metastasis. This evidence concerns the gene TGFB1 and breast cancer.