WM793 and 1205LU cells were transfected with the vector (V), WT Smad3 (WT) or the linker phosphorylation mutant of Smad3, EPSM Smad3 (M) expression vectors. A. 24 hours post transfection, whole cell lysates were prepared for the analysis of Smad3 expression and the linker phosphorylation at serine 208 and threonine 179 in the WM793 melanoma cells. GAPDH expression was used as a control. (B). In parallel, 24 hours post transfection, WM793 melanoma cells were incubated in the absence (−) or presence (+) of 200 pM of TGFβ for 48 hours and extracted for protein expression analysis of p15INK4B, p21WAF1 and PAI-1. (C). 24 hours post transfection, the transfected WM793 and 1205LU melanoma cells were incubated in the absence (−) or presence (+) of TGFβ for 72 hours and counted. Cell numbers (%) have been normalized with the number obtained for the vector-transfected cells. Each experiment is representative of 4 experiments done in triplicate.