LBH589 and Chk1 inhibitor treatment shows a synergistic effect in NSCLC cells.

<p><i>A</i>, A549 cells were treated with LBH589 40 nM and/or a UCN-01 (250 nM) for 24 hours, cell extracts were prepared, and Western blot analysis was performed with PARP (t: total, c: cleaved). Experiments were repeated at least 3 times, and a representative experiment is shown. <i>B</i>, A549 cells were treated with LBH589 and UCN-01 either alone or in combination at a constant ratio (1∶40) for 72 hours. Drug concentrations are indicated on the horizontal axis and plotted against cell viability of control wells, which was arbitrarily set at 100% viability for each experiment. Error bars represent ± SD of 4 replicate wells. <i>C</i>, combined effects of LBH589 and Chk1 inhibitor UCN-01 were quantified with the Chou and Talalay combination index (CI) method (40). The CI used for drug combination analyses was determined by the isobologram equation (see text). Ranking symbols (+/−) indicate average calculated Chou and Talalay combination index (CI) range (+++, strong synergism).