Figure 7. Metabolic aspects of myeloid differentiation. (A–D). Human acute myeloid leukemia HL-60 cells were treated with 10 μM erlotinib (ERLO), 10 µM PP2, 10 μM SB203580 (SB203), or an equivalent volume of DMSO, alone or in combination with 50 nM 1α,25-hydroxycholecalciferol (VD), for 7 d, then processed for the cytofluorometric detection of DNA and RNA content, upon Hoechst 33342/Pyronin Y co-staining (A and B) or the colorimetric detection of senescence-associated β-galactosidase activity (C and D). Representative dot plots and images are reported in (A) (numbers refer to the percentage of cells exhibiting a 2n DNA content and reduced RNA levels) and (C) (scale bar = 5 µM; arrows indicate senescent cells), respectively. Panels (BandD) report quantitative data on the percentage of Pyronin Y^low cells in the G₀/G₁ phase of the cell cycle or cells expressing senescence-associated β-galactosidase, respectively (means ± SEM; n = 3). **P < 0.01, ***P < 0.001 (ANOVA plus Dunnett post-hoc test), as compared with DMSO-treated cells; +++P < 0.001 (ANOVA plus Bonferroni post-hoc test), as compared with VD-treated cells.