Figure 1.

Effect of parthenolide (PT) on the induction of HL-60 cell differentiation produced by 1,25-(OH)₂D₃. HL-60 leukemia cells were simultaneously treated with 5 nM 1,25-(OH)₂D₃ alone or in combination with various concentrations of PT for 72 h (A), or with 10 μM PT for various periods (B). Then, the cellular differentiation was assessed by the NBT reduction assay. The results are represented as the mean±s.e.mean (n=3). *P<0.01, relative to a group treated with 1,25-(OH)₂D₃ alone. **P<0.0001, relative to any other groups.