Fig. 1

Differential effects of doxorubicin on SKN-SH wild-type (W) and SKN-SH/Dox6 drug-resistant (R) human neuroblastoma cells. (A) Cytotoxic response of W and R cells to doxorubicin. Cells were incubated with doxorubicin for 72 hr, after which cell viability was determined by the MTT assay. (B) DNA degradation following incubation of W and R cells with doxorubicin (1 µM) for 24 hr. Equal amounts of DNA were electrophoresed on 1% agarose gel. DNA fragments were stained with ethidium bromide and visualized under UV light. (C) Caspase-3 activity in W and R cells. Cells were treated with doxorubicin (1 µM) for 24 hr and caspase-3 activity assayed in the cell lysate. Note that caspase-3 activity correlates with DNA degradation shown in Panel B. Data are expressed in arbitrary units (AU) and represent the mean 6 SEM of triplicate determinations.