Cbl-70Z and Flt3 synergize to induce autonomous growth. (A,B) Cbl-70Z induces ligand-independent proliferation and survival of 32D-Flt3-WT cells. The 32D cells overexpressing the indicated Flt3 and or Cbl proteins were grown in the presence of 10% FCS alone or supplemented with FL or IL-3. Cells were counted at the indicated time points by the trypan blue exclusion method. The data are shown as fold change of the cell number compared with the start of the experiment (panel A). (B) The proportion of cells in the culture that was alive is shown. The data represent the average and standard deviation of 3 independent experiments. (C) Ligand-independent DNA synthesis of Flt3-WT cells coexpressing Cbl-70Z. The 32D cells overexpressing Flt3-WT and/or Cbl constructs were starved from IL-3 and proliferation was measured in [³H]-thymidine incorporation assays. Data are shown as percentage of thymidine incorporation relative to the thymidine incorporation of the respective cell line with IL-3 supplementation. (D) The Flt3-specific inhibitor SU11248 inhibits proliferation of Cbl-70Z–coexpressing 32D-Flt3-WT cells. Proliferation of 32D cells expressing Flt3-WT with or without Cbl-70Z was analyzed as in panel C.