CEM-C1-15 cells that survive treatment with MAPK inhibitors plus Dex remain sensitive upon retreatment. CEM-C1-15 cells were treated with vehicle (Control), Dex, U0126 (U) and SP600125 (SP) in the combinations shown (Initial). After 96 hours, the drugs were diluted by centrifugation, washed, and the cells immediately reincubated in fresh growth medium. The drug combinations were then reintroduced (Retreat). At the time points shown, viable cells were counted by trypan blue dye exclusion assay, n = 2. Ordinate, note log scale.