β-sitosterol is a phytosterol previously studied for its anti-cancer effects; it was shown to have anti-proliferative and pro-apoptotic effects on U937 cells by selectively activating caspase-3 and increasing the Bax/Bcl-2 ratio, whereby the addition of z-DEVD-fmk (a caspase-3 specific inhibitor) or the overexpression of Bcl-2 significantly attenuated the apoptotic response [34]. The gene discussed is CASP3; the disease is cancer.