Hydrogen peroxide inhibits the growth of lung cancer cells via the induction of cell death and G1-phase arrest

Hydrogen peroxide (H₂O₂) is frequently applied to cultured cells to induce oxidative stress. The present study investigated the molecular and cellular effects of exogenous H₂O₂ on Calu-6 and A549 lung cancer cells. Based on MTT assays, H₂O₂ inhibited the growth of Calu-6 and A549 cells with IC₅₀ values of ~50 and 100 µM at 24 h, respectively. Cells treated with H₂O₂ demonstrated a considerable G1-phase arrest of the cell cycle. H₂O₂ dose-dependently augmented the numbers of dead (trypan blue-positive) and Annexin V-FITC-stained cells in these cells, which was accompanied by the reduction of Bcl-2 and pro-caspase-3 levels, as well as the upregulation of caspase-3 and -8 activities. In addition, H₂O₂ triggered the failure of mitochondrial membrane potential (MMP; ??_m). However, relatively higher doses of H₂O₂ did not raise the percentages of sub-G1 cells in these cell lines. All the tested caspase inhibitors (Z-VAD for pan-caspases, Z-DEVD for caspase-3, Z-IETD for caspase-8 and Z-LEHD for caspase-9) decreased the percentages of sub-G1 and Annexin V-FITC-stained cells in the H₂O₂-treated Calu-6 and A549 cells. However, caspase inhibitors did not significantly prevent the loss of MMP (??_m) in H₂O₂-treated lung cancer cells. In conclusion, H₂O₂ inhibited the growth of Calu-6 and A549 lung cancer cells through cell death and G1-phase arrest. H₂O₂-induced cell death resulted from necrosis, as well as caspase-dependent apoptosis.