Figure 1.

Cardiac glycosides induce cancer cell death by apoptosis. (a) Induction of cancer cell death by oleandrin. Cells were incubated in different concentrations of oleandrin for 24 h, and assayed for cell death by release of LDH. Assays were performed in triplicate (*P < 0.05, relative to 10 nM concentration point). Data are representative of three independent experiments. (b) Induction of cancer cell death by digitoxin. Cells were incubated in different concentrations of digitoxin for 24 h and assayed for cell death by release of LDH. Assays were performed in triplicate (*P < 0.05, relative to 50 nM concentration point). Data are representative of three independent experiments. (c) Drug concentration-dependent activation of caspases and PARP. Cells were incubated for 16 h in different concentrations of either oleandrin or digitoxin. Cells were then collected and subjected to Western blot analysis with antibodies against antigens as shown. (d) Time dependent changes in activation of caspases and PARP. Cells were incubated for different times in maximal concentrations of oleandrin (100 nM) or digitoxin (500 nM). Cells were then collected and subjected to western blot analysis with antibodies against antigens as shown