Rapid generation of a lethal human AML in NRG-3GS mice transplanted with MYC-transduced human CD34⁺ CB cells. (A) General experimental design. (B) Distributions of 12-day clone sizes from 238 MYC-GFP and 256 control-YFP–transduced cells sorted and plated 2 days after transduction in single-cell, cytokine-containing suspension cultures; 2 experiments, 2-tailed Mann-Whitney test, P < .0001. (C) Weekly nonadherent cell outputs in cultures containing human cytokine-producing stromal cells, normalized to the cell input numbers (4.5 × 10³MYC-GFP– or control-YFP–transduced cells). (i) Results when these were cultured separately. Insets are Giemsa-stained cytospins of week 8 cells. (ii) Results when the same numbers of MYC-GFP– and control-YFP–transduced cells were cultured together in the same wells. Mean ± standard error of the mean of replicate cultures from 1 of 2 experiments with different CB cells; 2-way analysis of variance. (D) Survival of NRG-3GS recipients of 0.6 to 2 × 10⁴MYC-GFP–transduced cells or 1 to 3 × 10⁴ empty-vector GFP-transduced (control) cells; log-rank test, P < .0001. Inset shows Giemsa-stained touch preps of spleen cells at 3 weeks after transplant. (E) GFP chimerism in the BM of recipients of MYC (n = 6) or control (n = 4) cells 3 to 5 weeks after transplant. (F) Phenotype of GFP⁺ cells shown in panel E; unpaired 2-tailed Student t test. MYC, red; control, steel blue. Scale bars in photomicrograph insets are 10 μm.