Effect of c-Jun expression on the proliferation and cell cycle of MCF-7 cells. A, proliferation assay. Cells (3.5 × 103/well) were cultured for continuous five days and proliferation of MCF-7/c-Jun cells was measured in an MTT-based assay. ** P < 0.01 B and C, cell cycle analysis. MCF-7 cells were washed with cold PBS and fixed in cold 70% (v/v) ethanol at 4°C for at least 18 hours. Then the cells were incubated with RNase A (100 μg/ml) at 37°C for 30 minutes and stained with propidium iodide (PI) (50 μg/ml) in the dark at 4°C for 20 minutes. DNA content was measured by flow cytometry. Striped column, G0-G1 phase; empty column, G2-M phase; solid column, S phase.