Western blot analysis of the cell-cycle–associated proteins Rb, p21 ^CIP1/WAF1, p27^KIP1, CDK2, CDK4, cyclin D1, cyclin D2, cyclin D3, cyclin E, and p15^INK4.

Total cellular proteins (15 μg/lane) were separated on 12.5% SDS-polyacrylamide gels and transformed to the membrane. For the analysis of Rb, 7.5% gels were used. Protein levels were detected by means of Western blotting with antibodies directed against each protein. pRb indicates hypophosphorylated Rb; ppRb, hyperphosphorylated Rb. Blots were stained with Coomassie brilliant blue to confirm that equal amounts of protein were present in each lane.