Induction of differentiation of THP-1 and HL60 cells by combined treatment with retinoid and 1,25(OH)₂D₃.

(A) NBT-reducing activities. Cells were treated with vehicle control (Cont), 100 nM 9cRA, ATRA, Am80 or HX630 in the absence or presence of 100 nM 1,25(OH)₂D₃ (D3) for 5 days. *, p<0.05; **, p<0.01; ***, p<0.001 (one-way ANOVA followed by Tukey’s multiple comparisons). (B) Morphological changes of THP-1 and HL60 cells treated with 9cRA and/or 1,25(OH)₂D₃. Cells were treated with vehicle control (Cont), 100 nM 9cRA and/or 100 nM 1,25(OH)₂D₃ for 5 days and the cell smears were stained with May-Grünwald-Giemsa. (C) Cell proliferations. Cells (1×10⁵/ml) were cultured with vehicle control (Cont), 100 nM 9cRA and/or 100 nm 1,25(OH)₂D₃ (D3), and cell numbers were counted at indicated days. *, p<0.05; **, p<0.01; ***, p<0.001 vs Cont; ###, p<0.001 vs 9cRA; +++, p<0.001 vs D3 (one-way ANOVA followed by Tukey’s multiple comparisons). †††, p<0.001 (two-way ANOVA).