Clonogenesis by HPC transduced with the indicated vector.

(A, top) Morphology of the colonies generated by 100 HPCs stimulated with multilineage HGFs (see “Materials and Methods”), expressed as a percentage of the total number. Mean ± SD values from 5 experiments. The total number of colonies ± SD was 52 ± 7.1 for control (GFP) and 50 ± 5.5 for PML/RARα cells. (A, bottom) Analysis of the erythroid colonies in multilineage cultures: 40% of the cells within CFU-GEMM colonies and 62% of the cells within CFU-GM colonies were promyelocytes. (B) Morphology of the colonies generated by unilineage HGF stimuli (see “Materials and methods” and Grignani et al21). E, BFU-E; G, CFU-G; Mo, CFU–monocytic; Mk, CFU–megakaryocytic; Pro, promyelocytic colonies. Mean ± SD values from 5 experiments. The numbers of seeded cells/plate were 100 for BFU-E and CFU-G, 500 for CFU-MK, and 1000 for CFU-Mo. The mean number of colonies/plate ± SD generated by GFP cells were 25.4 ± 4.4 BFU-E, 12.5 ± 2.3 CFU-G, 15.6 ± 2.1 CFU-MK, and 17.8 ± 1.8 CFU-Mo. The total number of colonies generated by PML/RARα cells was 19.6 ± 1.8 BFU-E/promyelocytic, 13.6 ± 2.1 for CFU-G/promyelocytic, 18.4 ± 3.2 CFU-MK/promyelocytic, and 19.5 ± 3.1 CFU-Mo/promyelocytic. Asterisks above the columns indicate statistically significant differences between GFP and PML/RARα samples as calculated from a Student 2-tailed t test. *P < .01; **P< .001.