Cotreatment with LBH589 and 17-AAG induces more apoptosis and exerts synergistic cytotoxic effects in K562 and MV4-11 cells. (A, C) K562 (A) and MV4-11 cells (C) were treated with the indicated concentrations of LBH589 and/or 17-AAG for 48 hours. Following this, the percentage of annexin-V-stained apoptotic cells was determined by flow cytometry. (B, D) Using Calcusyn software (Biosoft), the analysis of the dose-effect relationship for LBH589 and/or 17-AAG-induced apoptosis of K562 (B) and MV4-11 (D) cells was performed according to the median effect method of Chou and Talalay.33 The combination index (CI) values were calculated for 3 independent experiments. CI<1, CI=1, and CI1 represent synergism, additivity, and antagonism of the 2 agents, respectively.
