Influence of c-kit cDNA transduction on the size of colonies derived from CD34⁺⁺⁺ cells in the presence of full dosages of IL-3, GM-CSF, Epo, and SLF (10 ng) per mL. The 30 largest CFU-GM, BFU-E, and CFU-GEMM colonies fromc-kit–cDNA or mock-transduced cells were removed from a total of 2 experiments and the cell numbers per colony were counted. Significant differences from mock virus control are:^aP < .0001; ^bP < .05.