Fig. 3.

Induction of HOXB4 activity protects cultivated HSCs from the negative effects TNF-α on stem cell self-renewal. (A) Experimental design to test the effect of TNF-α on the multilineage hematopoietic reconstitution capacity of HOXB4ER-expressing LSK cells in a competitive transplant setting. The progeny (expansion equivalent) of 2,000 HOXB4ER-transduced and 2,000 control vector (tCD34)-transduced LSK cells were mixed and cocultured, as indicated, in serum-free cytokine-supplemented medium in the presence or absence of TNF-α or FCS ± HOXB4 induction with TMX. After 7 days, the frequency of HOXB4ER-expressing and tCD34-expressing LSK cells in the resulting cell populations was determined by flow cytometry, and the cell samples were transplanted into cohorts of lethally irradiated recipient mice. (B) Reconstituting activity of HOXB4ER-expressing (■) and tCD34-expressing (▵) cells cultivated for 7 days, as indicated. Small horizontal lines indicate the median percentage of HOXB4ER⁺ or tCD34⁺ cells in the peripheral blood of the mice 11 weeks after transplantation.