2006-PO inhibits erythroid growth in the early stages of development. (A) Kinetics of erythroid growth. CD34⁺ cells were cultured in erythroid medium with (●) or without (○) 2006-PO. At the indicated days, the cells were collected, washed, and counted. The total cell yields are represented as a percentage relative to the total number of cells without 2006-PO on the seventh day (4.9 ± 0.2 × 10⁵ cells, n = 3). Insets: Amplification of the y-axis. (B) CD34⁺ cells were cultured for 7 days in erythroid medium. At the indicated days, 2006-PO was added to the medium. The total cell yields are represented as a percentage relative to the total number of cells without 2006-PO (7.4 ± 3.8 × 10⁵ cells, n = 3). (C) Effects of 2006-PO on CFU-E. CD34⁺ cells were cultured in erythroid medium. After 7 days in culture, the cells were collected and washed, and then cultured for a further 5 days (until day 12) in the presence of EPO, with or without 2006-PO. (A-C) Data are mean ± SD of 3 independent experiments. (D) Purified CD34⁺ cells were cultured in semisolid medium with IL-3, SCF, and EPO, with or without ODN. After 14 days in culture, the clots were observed directly (top panel) and then fixed and stained for hemoglobin (bottom panel). (E) BFU-E and small erythroid colonies were then differentially counted under light microscopy. The number of colonies is a representative of 2 independent experiments and the mean ± SD of triplicate culture. *P < .05. ***P < .001. NS indicates no significance.