DNA Fragmentation Analysis DNA fragmentation
served as a late apoptosis marker18) was detected by agarose
gel electrophoresis. Briefly, HeLa cells (1106 cells/ml)
were treated with 0.1% DMSO or with rhinacanthone, b -
lapachone and adriamycin (6m M) for 4 and 8 h. At the end
of incubation, cells were harvested and lysed in 20m l lysis
buffer (50mM Tris–HCl, pH 7.4; 10mM EDTA and 0.5%
sodium N-lauroylsacosinate). The lysate was incubated sequentially
with 500m g/ml ribonuclease A at 50 °C for 30 min
and 500m g/ml proteinase K at 50 °C for 60 min in a shaking
water bath. Equivalent amounts of DNA (2—3m g) were
electrophoresed on a 2% agarose gel in TBE buffer (2mM
EDTA, pH 8; 89mM Tris–HCl and 89mM boric acid) at 50V.
DNA fragments were visualized and photographed under
transmission UV light after being staining with 0.5m g/ml
ethidium bromide