DNA Fragmentation Assay for Apoptosis

DNA fragmentation was assessed by electrophoresis of genomic DNA extracted from K562 cells as described previously (Muller et al., 1996). Briefly, K562 cells (2 × 10⁶/ml) treated with cedrol for 18 h were harvested and homogenized with 50 μl of lysis buffer (50 mM Tris–HCl, 1% NP-40, 20 mM EDTA). The supernatant collected from whole-cell lysate was treated with 5 μg RNase A and 1% SDS for RNA digestion at 56°C for 2 h, subsequently with 2.5 μg/μl proteinase K for protein digestion at 37°C for 2 h. DNA was precipitated using 10 M ammonium acetate and ethanol, dissolved in gel loading buffer, and electrophoresed on 1% agarose gel with ethidium bromide staining.