Synergistic suppression of T-ALL growth with rapamycin and GSI. GSI-sensitive cell lines (left panel) and -resistant cell lines (right panel) were cultured in the presence of varying concentrations of GSI (compound E), rapamycin, or combination of both drugs at a fixed molar ratio of 1000:1 (compound E/Rapamycin). The number of viable cells in each well was determined using a MTS-based assay at the end of a 5- or 6-day incubation period. See “Materials and methods” for details in the calculation of “fraction affected” and combination index (CI). Error bars represent standard deviation. Lines are placed at 0.25 to facilitate comparisons between graphs.