TGF-β Signaling in Breast Cancer Cell Invasion and Bone Metastasis

The contribution of transforming growth factor beta (TGF-beta) signaling to breast cancer has been studied for more than two decades. In an early phase TGF-beta may act as a tumour suppressor, while later, when cells have become resistant to its anti-mitogenic effects, the role of TGF-beta switches towards malignant conversion and progression. TGF-beta stimulates cell invasion and modifies the microenvironment to the advantage of cancer cells. Studies have shown that TGF-beta promotes bone and lung metastasis via different mechanisms. The therapeutic strategies to target the TGF-beta pathway in breast cancer are becoming increasingly clear. This review will focus on the role TGF-beta in breast cancer invasion and metastasis.