Sensitizing effect of SAHA to death receptor–induced apoptosis.

(A) MM.1S cells were pretreated with the indicated concentrations of SAHA for 6 hours and then treated with low concentrations of TRAIL/Apo2L (50 ng/mL, ●), the Fas-activating antibody CH-11 (25 ng/mL, ▴), or vehicle (▪) for additional 18 hours. Error bars represent SD. (B) SAHA down-regulated the antiapoptotic proteins FLIP, cIAP2, and XIAP, which regulate death receptor–mediated apoptotic signaling.