TPEN-dependent cell death is partially due to apoptosis induction. A) Cleavage of PARP, caspase-3 and degradation of XIAP in TPEN-treated cells was reversed by the addition of z-VAD-fmk or ZnSO4. B) MTT viability assay in control (-) and TPEN-treated (+) cell in the presence of either z-VAD-fmk to inhibit caspases or ZnSO4 (mean ± SD, n = 3). C) Annexin and TUNEL assays under similar condition as in panel A) (mean ± SD, n = 3). *p < 0.05 and ** p < 0.01, significant difference with respect to TPEN.