Effect of p38 inhibitor SB203580 and ERK inhibitor UO126 on apicidin-mediated induction of HbF synthesis in K562 cells.

Cells were cultured for 4 days in the presence of 0.5 μM apicidin (gray and black bars) or 0.1% (vol/vol) DMSO (white bars). p38-specific inhibitor SB203580 (black bars) or ERK pathway inhibitor UO126 (gray bars) were added in increasing concentrations 1 hour prior to apicidin. After harvesting, cells were lysed, and HbF, total Hb, and total protein concentrations were determined. HbF per total protein (A) and HbF per total hemoglobin (B) were calculated as indicated. Cell numbers relative to untreated control cells (100%) are depicted in (C). Each experiment was performed 4 times, and standard errors were calculated as shown in the figure.