TPEN induces ROS generation in HCT116 cancer cells. A) Time course of TPEN-induced ROS generation in HCT116 and NCM460 cells. Control (Con) represents cells that have been treated with carrier DMSO. ROS generated in response to 250 μM H2O2 is also shown (mean ± SD, n = 3). B) Same data as in panel A) normalized to maximum levels of ROS induced in either the HCT116 or the NCM460 cells. Time zero represents carrier alone treatment and was set at zero. C) Cell viability in cells treated with TPEN in the presence or absence of the antioxidants NAC or vitamin E (mean ± SD, n = 3). D) Apoptosis measured using the TUNEL and Annexin assays in cells treated with TPEN in the presence and absence of NAC (mean ± SD, n = 3). ** p < 0.01, significant difference with respect to TPEN in C, and D, and with respect to control in A.