Figure 4. Variability in cytokine-dependent long-term expansion of AML CD34⁺ cells on MS5 stroma.

4×10⁵ AML CD34⁺ cells were sorted and plated in 12-well plates precoated with MS5 stromal cells. Cells were expanded in LTC medium supplemented with 20 ng/ml IL-3, G-CSF, TPO, combinations thereof, or without any cytokines. Cultures were demi-depopulated weekly for analysis. Weekly cumulative cell counts represented cells in suspension. The cytokines above the figures indicate which cytokines were able to induce STAT5 phosphorylation. c.a. indicates constitutive activation of STAT5.