Table 1.

Induction of γH2AX and ATM-S1981^P by smoke from 2R4F and T&N-free cigarettes in relation to the cell cycle phase

Smoke	G1	S	G2M
	γ H2AX
2R4F whole smoke	4.51 ± 0.65	4.14 ± 0.54	2.63 ± 0.27
T&N-free whole smoke	7.60 ± 0.44	4.35 ± 0.15	4.56 ± 0.19
T&N-free vents	4.54 ± 0.65	3.90 ± 0.02	3.18 ± 0.11
T&N-free vapor	6.04 ± 0.02	4.18 ± 0.14	4.14 ± 0.60
	ATM-S1981P
2R4F whole smoke	2.92	3.09	2.84
T&N-free whole smoke	5.55	4.83	4.32
T&N-free vents	3.99	4.23	3.81
T&N-free vapor	5.14	4.71	4.09

A549 cells were exposed for 20 min either to whole 2R4F smoke or to whole smoke, smoke from cigarettes having air dilution holes (vents) or to the vapor phase (vapor) of T&N-free cigarettes and then incubated for 1 h, as described in Materials and Methods. The mean values of γH2AX (±SE, n = 4) and ATM-S1981^P IF intensity (integral) for cells gated in G₁, S and G₂M phases of the cell cycle are presented as n-fold increase over the mean values of the mock-treated cells in the respective phases of the cell cycle.