A, MiaPaCa-2 and Panc-1 cells were treated with various concentrations of LB100, as indicated, for 2 hours. Cells were then harvested and PP2A activity was assayed as described in Materials and Methods. B, Cells were treated with 1 or 3 μmol/L LB100 and radiation as indicated and then assessed for clonogenic survival. Plots shown are representative of 2 – 3 independent experiments. Data in the legend are the mean RER ± SD (n = 2 – 3). The mean cytotoxicity of siRNA treatments was 1.0 (Ctrl), 0.9 (1uM), and 0.8 (3uM) in MiaPaCa-2 and 1.0 (Ctrl), 0.9 (1uM), and 0.7 (3uM) in Panc-1 cells with less than 10% SD. Statistically significant differences versus control* are indicated.