Transforming growth factor-β (TGF-β) is a multifunctional regulator of
cell growth, apoptosis, differentiation, and migration. TGF-β1 was
originally discovered as a secreted protein that induces
anchorage-independent growth in normal rat kidney NRK49F fibroblasts
in the presence of epidermal growth factor (EGF). TGF-β was shown to
potently inhibit the proliferation of most cell types, including
epithelial cells, endothelial cells, hematopoietic cells, and
lymphocytes, and is widely known as a tumor suppressor. Studies
investigating TGF-β signaling have revealed that perturbations of the
TGF-β signaling pathway, such as mutations of TGF-β receptors or Smad
proteins, lead to cancer progression and are related to poor prognosis
of certain types of cancer. However, recent findings have shown that
cancer cells become resistant to the growth inhibitory activity of
TGF-β and that TGF-β facilitates invasion and metastasis of these
cells both in vitro and in vivo.
(Miyazono et al., 2013, Upsala Journal of Medical Sciences)