Thalidomide-induced γ-globin expression requires enhanced ROS and mediated p38 MAPK activation. CD34⁺ cells grown in EPO medium for 6 days were treated with 100 μM thalidomide in the presence or absence of the antioxidants catalase (4000 U/mL) or DMTU (10 mM) or the p38 MAPK inhibitor SB203580 (5 μM) from days 6 to 14. RNA extracted from cells harvested on day 14 was amplified by quantitative PCR to determine γ- and β-globin expression levels. (A) Average copy number of γ-globin molecules per 1 ng total RNA. (B) Average copy number of β-globin molecules per 1 ng total RNA. (C) Average ratio of γ/γ + β-globin percentages. Results are shown as means (± SD) from 3 independent donors that were analyzed in separate experiments. *P < .05 versus untreated cells.