Transforming growth factor-β signaling in tumor initiation, progression and therapy in breast cancer: an update

Transforming growth factor-beta (TGF-beta) is a ubiquitous cytokine playing an essential role in cell proliferation, differentiation, apoptosis, adhesion and invasion, as well as in cellular microenvironment. In malignant diseases, TGF-beta signaling features a growth inhibitory effect at an early stage but aggressive oncogenic activity at the advanced malignant state. Here, we update the current understanding of TGF-beta signaling in cancer development and progression with a focus on breast cancer. We also review the current approaches of TGF-beta signaling-targeted therapeutics for human malignancies.