Detection of phosphorylated histone (γH2AX) foci in human mammary epithelial cells (HMECs) to estimate DNA damage.
A. Endogenous γH2AX foci: the proportion of cells containing ≥1 foci in late PD cells is significantly higher than in early PD cells (p<0.0001, Chi-squared test). The foci were counted in 1000 cells per sample. B. Mean incidence of γH2AX foci per cell 2 h after mammogram X-ray exposures is greater in the late PD HMECs in each of the three donors analyzed. The foci were counted in 2000 cells (donor 1) and 1000 cells (donor 2 and 3) per group. Error bars signify standard error. Asterisk denotes statistically significant difference in a group of irradiated HMECs compared to the shamirradiated controls of each cell subpopulation (Mann Whitney test). Simple asterisk (*) refers to statistically significant difference p<0.01 and double asterisk (**) refers to highly significant difference p<0.0001. C. Representative images of γH2AX foci in HMECs from early and late PD exposed to 0, 2 and 10 automatic X-ray shots under a mammogram device (2 hours post-irradiation). Arrowheads point to the γH2AX foci stained in red. In vitro aged populations exhibited a higher number of γH2AX foci compared to the young counterparts.