Pim deficiency sensitizes v-Abl–transformed cells to undergo apoptosis. (A) v-Abl–transformed wild-type (WT) or Pim-1^−/−/Pim-2^−/−/Pim-3^−/− (TKO) cells were treated with imatinib at indicated times. Apoptosis and cell survival were analyzed by the propidium iodide/Annexin V binding and measured by flow cytometry. Plotted are the results from 3 independent experiments. (B) v-Abl–transformed wild-type or TKO cell lines were analyzed by Western blotting with indicated antibodies. (C) Blots in panel B were quantitated as in Figure 4. Plotted are the average levels of Bcl-XL and Bcl-XS from 3 independent experiments. (D) v-Abl–transformed wild-type or TKO cells were treated with imatinib in a time course. Lysates from these cells were analyzed by immunoblotting. Blots were then quantitated as described above. The average levels of Bcl-XL and Bcl-XS from 3 independent experiments are plotted such that the protein level at 0 hour time point is 100%. Error bars represent SD.