Figure 4

Radiation induced H2AX phosphorylation in MCF-7 monolayer and mammosphere cells. (a) Unirradiated cells or cells exposed to 1 or 10 Gy γ-radiation and then incubated for one hour at 37°C, or (b) cells exposed to 1 Gy and incubated at 37°C for different times, were fixed, permeabilized and immunostained with an antibody to γH2AX and counter-stained with 4',6-diamidino-2-phenylindole (DAPI). H2AX phosphorylation was clearly visible as characteristic fluorescent foci in the irradiated monolayer cells, but no foci were detectable in the irradiated mammosphere cells.