LCL161/LBH589 (panobinostat) synergistically induces apoptosis in MM.1S cells. (A) MM.1S cells were exposed (24 hours) to 5 µM LCL with or without 5 nM LBH, followed by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) staining (left panel) using fluorescence microscopy (bar = 40 µm). The percentages of TUNEL (+) cells are presented in the right panel. (B) MM.1S cells were exposed (24 hours) to varying concentrations of LBH ± LCL at a fixed ratio (1: 2000), after which the percentage of 7-AAD⁺ cells was determined. Combination index values <1.0 denote a synergistic interaction. (C) MM.1S cells were exposed to the indicated concentrations of LBH ± LCL for 24 hours, followed by flow cytometric analysis of cell death after staining with 7-AAD. (D) MM.1S cells were incubated with LBH ± LCL for 24 hours. Caspase-3 and PARP were monitored by immunoblotting analysis. β-actin was assayed to ensure equivalent loading and transfer. *P < .05, **P < .01. All experiments were repeated three times. CF, cleavage fragment; DAPI, 4′,6-diamidino-2-phenylindole.