TGFB1 and breast cancer: Enforced expression of Jagged1 in SMAD4-knockdown breast cancer cells, which are severely impaired in their ability to form productive osteolytic bone metastases due to the defective reception of microenvironment TGF-β cues (Kang et al, 2003, 2005), restored the bone metastasis-promoting functions of these malignant cells.