Cell cycle effects of tamoxifen, NU2058 or NU6102 on asynchronously growing MCF7 cell lines. (A) Representative western blot of cyclin D1, p21Waf1/Cip1, p27Kip1, ppRb T821 and total pRb protein levels in asynchronously growing MCF7, MMU2 and LCC9 cells exposed to 2 or 8 μ M tamoxifen, 25 or 75 μ M NU2058 and 5 or 15 μ M NU6102 for 24 h and compared with 0.1% (v/v) DMSO control. (B) E2F activity in cells transfected with an E2F luciferase reporter construct and a β-gal reporter plasmid. Relative luciferase activity was then expressed as a percentage of the DMSO-treated control. Data are mean±s.e. of three independent experiments. (C) Flow cytometric analyses of cells treated with tamoxifen and cyclin-dependent kinases-1/2 (CDK2/1) inhibitors expressed as the mean G1 (solid bar), S (open bar) and G2/M (grey bar) cell cycle fractions from three independent experiments.