SMAD1 and breast cancer: Here, we provide clinical and experimental evidence to illustrate the role of FOXF2 in breast cancer bone metastasis and uncover mechanisms underlying the osteomimetic formation and osteolytic bone metastasis of breast cancer cells, in which FOXF2 programs epithelium-to-osteomimicry transition (EOT) by pleiotropic transactivation of the BMP4/SMAD1 signaling pathway and bone-related genes that are expressed at early stages of bone differentiation.