Thalidomide induces activation of p38 MAPK and acetylation of histone H4. CD34⁺ cells were cultured in EPO alone medium for 7 days prior to the addition of thalidomide. (A) Cells were treated with different concentrations of thalidomide for 30 minutes. (B) Cells were treated with 100 μM thalidomide for the indicated times. Cellular protein (30 μg) was analyzed by Western blot using phosphorylated p38 MAPK and acetyl-histone H4 antibodies. The membranes were stripped and reprobed with total p38 MAPK and histone H4 antibodies as indicated to confirm that similar amounts of protein extracts were analyzed in each lane.