(A) Effect of overexpression of Id2 or its mutants in MCF-7 and SKOV-3 cells on [
H] thymidine incorporation into cellular DNA. The indicated cells transfected with the indicated plasmids were seeded in 24-well plates in culture media with 10% FBS (1 × 104/well). At the indicated times, [3H]-thymidine (2 μCi) was added to fresh medium and incubated for 1 h at 37°C prior to scintillation counting. Experiments at each time point were performed in triplicate, and the graph is representative of three independent experiments. (B) Effect of overexpression of Id2 or its mutants on proliferation rate of MCF-7 and SKOV-3 cells. The indicated cells transfected with the indicated plasmids were cultured in triplicate, and MTT assay was performed at the indicated times. Absorbance was examined at 590 nm by use of a microplate reader. Data are mean ± SEM for at least three separate determinations. CPM = counts per million; OD = optical density.