Figure 1

IR induces G ₂ /M cell-cycle arrest and Rac1 activation in MCF-7 cells. (A) Upper panel: log-phase growing MCF-7 cells were exposed to 5-Gy IR, incubated for the indicated hours, and analyzed for cell cycle by fluorescence-activated cell sorting (FACS). Amounts of cells in the G₁, S, and G₂/M phases of the cell cycle are indicated. Lower panel: MCF-7 cells were exposed to IR at the dose indicated, incubated for the indicated hours, and analyzed for DNA content. Results depict the percentage of cells with 4N-DNA content (G₂/M phase) and represent the mean ± SD of two sets of experiment in duplicate samples. * P = < 0.001 (n = 4), significant difference from control unirradiated cells. (B) Upper panel: MCF-7 cells were exposed to IR at the indicated doses, incubated for 24 hours, and analyzed for cell cycle with FACS. Percentage of cells in G₁, S, and G₂/M phases of the cell cycle are indicated. Lower panel: Cells were exposed to increasing doses of IR, incubated for 24 hours, and analyzed for DNA content with FACS. Results depict the percentage of cells with 4N-DNA content and represent the mean ± SD of triplicate samples. (C) MCF-7 cells were exposed to 20-Gy IR, incubated for the indicated times, and analyzed for Rac1 activity, as described in Materials and methods.