Effect of cyclin-dependent kinase-2 (CDK2), CDK1 and combined CDK2/1 siRNA on cell cycle profile and cell survival. (A) Representative examples of western blot showing CDK2 and CDK1 levels prepared 72 h post-transfection of either scrambled (Sc), CDK2 (K2), CDK1 (K1), CDK1 and CDK2 (K1/2) siRNA in asynchronously growing breast cancer cells. (B) Cell cycle analysis data pooled from three independent experiments expressed as the mean G1 (solid bar), S (open bar) and G2/M (grey bar) cell cycle fractions of cells treated as given in A. (C) Mean and s.e. of colony formation for cells treated as given in A; colony formation was assessed at 2 weeks post-transfection.