For H2O2 treatment (Sigma-Aldrich), cells were plated in a 96-well plate at 2000 cells/well. Medium was changed each day to normal growth 500 μM H2O2 containing medium. Cell density was measured using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT; Fisher Scientific) according to manufacturer’s protocol.