Figure 1.

Effects of sesquiterpene lactone compounds on ATRA-induced HL-60 cell differentiation. (a) Chemical structures of sesquiterpene lactone compounds used in this study. (b) HL-60 cells were treated for 72 h with 50 nM ATRA alone or in combination with increasing concentrations of each of the sesquiterpene lactones. (c) Cells were treated with 50 nM ATRA alone or in combination with 1 μM helenalin (HT) or 10 μM of costunolide (CT), parthenolide (PT) or sclareolide (SC), for various time periods. Cell differentiation was assessed by the NBT reduction assay. Each value represents the mean±s.e.mean (n=3). ^*P<0.01, relative to a group treated with ATRA alone. SLs, sesquiterpene lactones.