Cellular reducing condition enhances the effect of SCF. CD34⁺ cells cultured with or without SCF (50 ng/mL) in the presence or absence of the indicated concentration of NAC or 2-ME from day 6 to day 14. Total RNA was isolated, and quantitative real-time PCR was performed to analyze the expression of γ-globin mRNA under the reducing conditions (A), the expression of β-globin mRNA under the reducing conditions (B), the ratios of γ/(γ + β) globin percentages under the reducing conditions (C). Results are shown as mean ± SD from 3 independent donors that were analyzed in separate experiments. *P < .05 versus unstimulated cells.