SMAD3 and neoplasm: While these data are generally consistent with the tumour-suppressive functionality of SMAD3, the relatively modest effect of SMAD3 overexpression on single cell 3D outgrowth can be potentially explained by the possibility of the FLP-promoting effect (an outgrowth-promoting feature in single-cell outgrowth setting) partly negating the anti-proliferative action of SMAD3.