Effects of 5-azacytidine and decitabine on proliferation of neoplastic MCs and normal BM cells. (A) HMC-1.1 and HMC-1.2 cells were incubated in control medium (Co) or various concentrations of 5-azacytidine or decitabine (37°C, 96 hours). Thereafter, cell-cycle distribution was measured by flow cytometry using PI. The percentage of cells in G₀/G₁ phase (black bars), G₂/M phase (gray bars), and S phase (open bars) are shown. Results represent the mean ± SD of 3 independent experiments (*P < .05 compared with control). (B) HMC-1 cells were incubated in control medium (Co) or various concentrations of 5-azacytidine or decitabine at 37°C for 48 hours. Thereafter, ³H-thymidine uptake was determined. Results show the percentage of ³H-thymidine uptake compared with control (Co on x axis = 100%) and represent the mean ± SD of 5 independent experiments (*P < .05 compared with control). (C-D) Primary neoplastic cells from patients with systemic mastocytosis, SM (ISM, SM-CMML, and ASM [C]), or normal BM cells (D) were incubated in control medium (Co) or various concentrations of 5-azacytidine or decitabine (37°C, 48 hours). Then, ³H-thymidine uptake was measured. Results show percent ³H-thymidine uptake compared with control. Data obtained in HMC-1 cells (B) represent the mean ± SD from 3 independent experiments, and data obtained with primary cells (C-D) represent the mean ± SD from triplicates (*P < .05 compared with control).