Figure 7.

Effects of cyclin D1b on the transcriptional activity of ER and requirement for CDK4 activity in response to antiestrogen therapies. A, MCF-7 cells were cotransfected and treated as described in Materials and Methods with cytomegalovirus β-galactosidase reporter and ERE-Luciferase reporter plasmids. Cells were harvested and assayed for luciferase activity, which was normalized to β-galactosidase activity. Data are from three independent experiments. B, MCF-7 cells were cotransfected with H2B-GFP and indicated plasmids for 16 h. Then, cells were washed with PBS and replaced in phenol red–free DMEM containing 10% CDT with either 10⁻⁹ mol/L 4-hydroxy tamoxifen or 10⁻⁶ mol/L ICI for 36 h. Cells were pulsed with BrdUrd for 6 h, and BrdUrd incorporation was monitored via indirect immunofluoresence. Two independent experiments with at least 200 cells counted per experiment. Error bars, SD. *, P < 0.05 compared with vector.