(A) HEK293T cells were treated with 100 or 300 μM TBHP for 1.5 hour and the markers of NRF2 (NQO1), PERK (PERK-T, eiF2α -P), Cyclin D1 and its inhibitors (p15, p16, p21, p27) were followed by immunoblotting. GAPDH was used as a loading control. (B) Densitometry data represent the intensity of NQO1, PERK-T, Cyclin D1, p15, p16, p21 and p27 normalised for GAPDH and eiF2α-P normalized for total level of eiF2α. For each of the experiments, three independent measurements were carried out. Error bars represent standard deviation; asterisks indicate statistically significant difference from the control: * p < 0.05; ** p < 0.01. (C) The hypothetic control network of cell cycle regulatory system with respect to oxidative stress.