Table 1.
Relative frequencies of γH2Ax and 53BP1 foci per cell after exposure to UV (20 J/m2), UV plus caffeine (20 J/m2 and 1 mM caffeine), or etoposide (50 μM) in normal GM5659T cells
| γH2Ax foci | 53BP1 foci | γH2Ax and 53BP1 foci (coincident) | (γH2Ax + 53BP1)/γH2Ax | |
| Control | 3.6 ± 7.2 | 3.8 ± 5.0 | 2.6 ± 4.1 | 70.5% |
| UV | 11.3 ± 9.5 | 1.9 ± 3.8 | 1.7 ± 3.5 | 15.2% |
| UV plus caffeine | 11.4 ± 9.5 | 2.5 ± 4.6 | 2.3 ± 4.3 | 20.0% |
| Etoposide | 21.3 ± 8.7 | 15.0 ± 8.1 | 14.2 ± 7.8 | 66.4% |
Numbers were calculated from the mean numbers of foci per cell at 2, 4, and 8 h after exposure (Fig. 1B). The frequencies of total γH2Ax foci (first column) were subjected to paired comparisons and were significantly different (P < 0.0001) except for UV versus UV plus caffeine (P = 0.5712). The frequencies of coincident γH2Ax and 53BP1 foci (third column) were subjected to paired comparisons and were not significantly different (P < 0.0001) except for control versus UV plus caffeine, which had a marginal difference (P = 0.0495).