2.5. DNA Fragmentation Analysis (DNA Laddering)

After the treatment, the cells were lysed in lysate buffer containing 10 mM Tris-Cl (pH 8.0), 150 mM NaCl, 10 mM EDTA, 0.4% SDS, and 100 g/ml protease K. The cells were incubated at 37°C overnight with gentle agitation and extracted with phenol/CHCl3/isoamyl alcohol, followed by CHCl3/isoamyl alcohol. DNA fragmentation was detected by loading 10–20 µg of total DNA onto a 2% agarose gel in Tris-acetate/EDTA buffer and visualized by ethidium bromide staining as described previously [14].