TGF-ß signaling in breast cancer cell invasion and bone metastasis.

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