β-sitosterol, a plant sterol, induces apoptosis and activates key caspases in MDA-MB-231 human breast cancer cells

The objective of the present study was to evaluate the effect of β-sitosterol, a plant sterol that induces apoptosis in breast cancer cells, on two pathways leading to apoptosis. These pathways are classified based on the localization of the initiated signal, extrinsic and intrinsic pathways. Extrinsic and intrinsic pathways are catalyzed by caspases 8 and 9, respectively, which leads to the activation of the executioner caspase 3. The results of the present study indicate that β-sitosterol supplementation at 16 μM for 3 days to MDA-MB-231 cells induces 39% and 80% increases in the activities of caspases 8 and 9, respectively, compared to cholesterol supplemented cells or controls. There was also a 3-fold increase in the activity of caspase 3. Sterol treatment had no effect on the quantities of the enzymes. It is concluded that β-sitosterol may induce apoptosis through the two pathways but was more pronounced on the intrinsic pathway.