Effects of HGF on ROS accumulation. Serum-starved cells were treated with increasing concentrations of HGF (0, 10, and 40 ng/ml). After incubation for 1 h, the cells were incubated with DCF-DA (10 μM) for 10 min. The cells were washed with PBS, trypsinized, and resuspended in PBS. The intensity of DCF-fluorescence was immediately measured with a flow cytometer (A). Mean fluorescence intensity was obtained from 3 independent experiments and plotted (B). Representative data from 3 independent experiments were shown. Values are the means ± SD of three independent experiments. Statistical significance was estimated by Student's t-test (*, p < 0.05).