Impaired lymphomyeloid differentiation of human long-term repopulating cells overexpressing HOXB4 in NOD/SCID mice.

The FACS profile of the BM of a representative mouse receiving a transplant of HOXB4 (FMEV-HAHOXB4wPRE)–transduced cells (67.9% GFP⁺/CD34⁺ cells) is shown at 8 weeks after cell injection. Forward-scatter/side-scatter properties and propidium iodide staining were used to exclude dead cells from analysis. Human CD45⁺ cells were gated and analyzed for GFP marker gene expression. Subsequently, the proportion of primitive human cells (CD34⁺), myeloid cells (CD33⁺), and B-lymphoid cells (CD19⁺) were determined in the population of nontransduced human cells (R4: GFP⁻/CD45⁺), in the total population of HOXB4-transduced cells (R5: GFP⁺/CD45⁺), and in the subpopulation of transduced cells expressing HOXB4 at very high levels (R6: GFP⁺⁺⁺/CD45⁺). The frequency of lymphoid and myeloid differentiated cells was significantly lower in the compartment of HOXB4-transduced cells (all GFP⁺, central histogram panel) than in the nontransduced cell population (GFP⁻, left panel), whereas the frequency of primitive CD34⁺ cells was concurrently increased in the population of HOXB4-expressing cells. In particular, this altered lineage contribution was enhanced in the transduced cells expressing HOXB4 at very high levels (right panel).