Cell proliferation and clonogenic assays

To determine the average rate of population doublings, HeLa-LMP, HepG2-LMP, HeLa-shPRDX1 and HepG2-shPRDX1 cells were plated into 10 cm diameter petri-dishes in duplicate with initial cell density of 1.6 × 10⁶ cells/dish. After the indicated intervals (0 to 48 h), cells were trypsized and counted using the Countess^® Automated Cell Counter (Life Technologies). The numbers were converted into population doublings according to the following formula: [log (No. of cells counted)-log (No. of cell plated)]/log(2)⁶⁸.

For the clonogenic assay, the indicated cell lines were plated in 6 cm diameter plates 24 h prior to treatment with and without the indicated concentrations of H₂O₂ for 1 hr and the colony forming unit was performed as described previously⁶⁹.