Reduction of Bim-EL levels inhibits apoptosis in CM preleukemic cells. (A) Experimental design of Bim knock-down strategy. (B) Relative Bcl2l11 transcript levels (quantitative RT-PCR) in puromycin-selected NIH-3T3 (3T3) or sorted GFP⁺7-AAD^– CM preleukemic cells infected with either Scrambled shRNA (shScr) or Bim shRNA (shBim). *P < .05, **P < .01. (C) Western blot analysis of Bim-EL levels in puromycin-selected NIH-3T3 cells (left panel); quantification of Bim-EL protein levels normalized to Erk1/2 (right panel). A vertical line has been inserted to indicate a repositioned gel lane. (D) Western blot analysis of Bim-EL levels in sorted GFP⁺7-AAD^– CM preleukemic cells. (E) Quantification of apoptosis (Annexin V⁺/7-AAD^–) levels in c-kit⁺ GFP⁺ CM preleukemic cells infected with either Scrambled (shScr) or Bim (shBim) shRNA. **P < .01.