Figure 3. Representative example of the effect of treatment with p21+p16 siRNA on the protein levels of p21Cip1 and p16INK4a in HCEC cultured from a 71-year-old donor. A: Densitometric analysis of the effect of p21+p16 siRNA treatment on p21Cip1 protein expression in non-electroporated HCEC (-E/-siRNA), in HCEC electroporated with Silencer negative control #1 siRNA (+E/control siRNA), and in HCEC electroporated with p21+p16 siRNA (+E/p21+p16 siRNA). B: Western blots showing relative expression of p21Cip1 compared with beta-actin under each experimental condition. C: Densitometric analysis of the effect of p21+p16 siRNA treatment on p16INK4a protein expression under the same conditions as in A. D: Western blots showing relative expression of p16INK4a compared with beta-actin under each experimental condition. Results in A and C are expressed relative to beta-actin.