Effects of TT and 9CTT on the differentiation induced by ATRA or 9CRA in NB4 cells. The enhancing effects of TT and 9CTT on the NBT reduction induced by ATRA (A) and 9CRA (B) and those on CD11b expression in the cells induced by 9CRA (C) were examined. Cells (5 × 10⁴ cells/mL) were cultured with ATRA or 9CRA in the absence (•) or presence of 3 × 10⁻⁶ mol/L TT (▴) or 9CTT (▪) for 4 days. Values represent the means of three separate experiments. *P < .05, compared with the effects of TT.