Amelioration of anemia in mice with β-thalassemic hematopoiesis after in vivo selection of Pro140Lys MGMT/GFP-transduced hematopoietic cells. (A) PB Hb concentrations (g/dL) are shown for the control, untreated mice (▪) and the group of mice treated with TMZ/BG (▴). Mice not surviving the treatment are indicated (⋄). Values at 6 weeks (baseline), 18 weeks (6 weeks after the final drug treatment), and 30 weeks (12 weeks following the final drug treatment) after transplantation are shown. The mean baseline values of Hb concentration for the entire group of treated mice and the 5 mice that responded to drug treatment did not statistically differ from those of the untreated group of animals (P = .55 and P = .52, respectively). (B) Percentage of GFP⁺ RBCs at the indicated times after transplantation for the control, untreated mice (▪) and the mice treated with TMZ/BG (▴). Mice not surviving the treatment are indicated (⋄). The mean baseline values of GFP⁺ RBCs for the entire group of treated mice and the 5 mice that responded to drug treatment did not statistically differ from those of the untreated group of animals (P = .61 and P = .99, respectively). (C) In vivo selection of Pro140Lys MGMT/GFP⁺ RBCs in TMZ/BG-treated mice. FACS histograms for GFP expression in RBCs are shown for the indicated drug-treated mice. The percentage of GFP⁺ cells is indicated in the upper right corner of each histogram. The left panels show pretreatment baseline analyses and the right panels show posttreatment analyses at 18 weeks after transplantation. The solid lines indicate the profiles for the experimental mice, whereas the dotted lines indicate the profile for a normal, negative control mouse.