Direct transduction of recombinant degradation-resistant HOXB4 protein maintains G-CSF–mobilized CD34⁺ cells in a more primitive state than wild-type HOXB4. (A) Comparison of HOXB4 mRNA expression levels in CD34⁺ UCB cells vs CD34⁺ G-CSF–mobilized cells. (B-C) Comparison of granulocyte-monocyte colony-forming cells (CFU-GM), erythroid burst-forming cells (BFU-E), and erythroid colony-forming cells (CFU-E) after addition of wild-type or degradation-resistant recombinant HOXB4 protein to CD34⁺ G-CSF–mobilized cells. (D) Limiting dilution CAFC assays of G-CSF–mobilized CD34⁺ cells after addition of wild-type or degradation-resistant HOXB4 protein. (E) Multi-lineage engraftment of G-CSF–mobilized CD34⁺ cells treated with wild-type or degradation-resistant recombinant HOXB4 protein in NSG mice (n = 8 per group) 12 weeks post-primary transplantation. The experiment was independently repeated 3 times.