Background
In many cell types, transforming growth factor beta (TGFβ) results in a growth inhibitory signal, which is mediated by transducers of the Smad family. In tumour cells, however, TGFβ-dependent antiproliferative control is lost and cells acquire the ability to replicate in TGFβ-rich environments. Furthermore, molecular and clinical evidence points to a role for TGFβ signalling in cancer progression and metastasis; however, it is unclear at which points of the metastatic process TGFβ signalling occurs and whether it is necessary and/or sufficient to elicit cancer cell motility.