The stability of p21 is increased by PTEN-knockdown. a. Wild type ACHN cells as well as those stablytransfected with PTEN-shRNA or empty vector control were incubated with cycloheximide (CHX; 20 μg/ml) for the times indicated and immunoblotted with antibodies against p21 and β-actin. b. Graphical representation of the data from densitometric quantification of p21 and β-actin reported as ratio of p21/β-actin and normalized to the "0 CHX control" for each lane. A representative experiment of four done is shown.