p21 regulates TGFβ-induced downstream genes involved in cell invasion. A, SUM159 cells were transfected with Scr or p21 siRNA as well as p21 cDNA. Cells were then treated with or without TGFβ and the mRNA levels of indicated genes were analyzed by real-time PCR (error bars indicate SEM; n = 3 independent experiments). B, SUM159 cells transfected with Scr siRNA and p21 siRNA were treated with TGFβ for the indicated times. The mRNA level of TGFBI gene was measured by real-time PCR (error bars indicate SEM; n = 3 independent experiments). C, SCP2 cells were transfected with the indicated siRNAs. Cell invasion was assessed using the Transwell Invasion assay. D, Total cell number was counted by Image J and number of invaded cells was quantified (error bars indicate SEM; n = 3 independent experiments).