Kinase activity of Kit and Flt3 is dispensable for Cbl-70Z–mediated transformation. (A-B,D-E) Cbl-70Z induces ligand-independent proliferation and survival of KD 32D-Kit (Kit-KD, A-B) or 32D-Flt3 (Flt3-KD, D-E) cells. The 32D cells stably overexpressing Kit-KD or Flt3-KD and/or indicated Cbl mutants were starved from IL-3, and cells were grown in the presence of 10% FCS. Cells were counted at the indicated time points by the trypan blue exclusion method, and the data are shown as fold change of the cell number compared with the start of the experiment (A,D). (B,E) The percentage of cells in the culture that were alive at the indicated time points. (C,F) Ligand-independent DNA synthesis of KD Kit (Kit-KD) or Flt3 (Flt3-KD) cells coexpressing Cbl mutants. 32D-Kit-KD or 32D-Flt3-KD cells stably overexpressing the indicated constructs were starved from IL-3 for 12 hours, treated with the indicated cytokines, and proliferation was measured in ³[H]-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. (A-F) Data represent the average and SD of at least 3 independent experiments.