FIGURE 1.

p16 down-regulation does not affect cell proliferation in primary skin fibroblasts. A, HFSN1 cells expressing either control-shRNA (HFSN1C) or CDKN2A-shRNA (HFSN1p16sh) were seeded in E-16 plates and reincubated for 48 h. The proliferation rate was measured using the RTCA-DP xCelligence system. B, cell cycle analysis using flow cytometry. C, immunostaining using Ki-67 antibody. Scale bars, 50 μm. Labeling index for Ki-67 staining was determined for at least 500 cells per data point and expressed as mean ± S.D. of triplicate determinations. D, whole cell lysates were prepared from the indicated cells and used for immunoblotting using the indicated antibodies. The numbers below the bands indicate protein expression relative to total pRB and GAPDH.