Effects of 5-azacytidine and decitabine on expression of FAS (CD95) in neoplastic MCs. (A) Cord blood progenitor-derived MCs and HMC-1 cells were cultured in control medium (open histograms) or in the presence of 5-azacytidine (5μM) or decitabine (5μM; gray histograms) at 37°C for 96 hours. Thereafter, CD95 expression was analyzed by flow cytometry. As visible, the demethylating agents promoted FAS expression in neoplastic MCs but not in normal MCs. (B) HMC-1 cells were cultured in the absence (Co) or presence of 5-azacytidine or decitabine (each 5μM) for 48 hours (gray bars) or 96 hours (black bars). Then, expression of CD95 was analyzed by flow cytometry. Drug-induced up-regulation of CD95 was calculated from mean fluorescence intensities (MFIs) obtained with treated (MFIstim) and untreated (MFIco) cells, and is expressed as stimulation index = SI (MFIstim:MFIco). Results show SI values and represent the mean ± SD of 3 independent experiments (*P < .05 compared with control). (C) HMC-1 cells were exposed to various concentrations of 5-azacytidine or decitabine (1-20μM) at 37°C for 48 hours (gray bars) or 96 hours (black bars). Then, cells were washed and stained with antibodies against CD117/KIT and analyzed by flow cytometry. Drug-induced down-regulation of KIT was expressed as SI (MFIstim:MFIco). Results represent the mean ± SD of 3 independent experiments (*P < .05 compared with control).