Lack of evidence for a role of TNF-α or TRAIL in ES-MDS apoptosis. (A) Flow cytometry analysis of membrane TNF-R1, TNF-R2, DR4, DR5, and Fas in normal (□; n = 5) and ES-MDS-deriving (▦; n = 7) mononuclear cells (top), GPA⁺ cells (middle), and in erythroid precursors on day 10 in liquid culture (bottom; ^*P < .05). Results are mean (± SEM) ratios of fluorescence intensities (RFIs) between specific and isotype control antibodies. (B) Effect of TNF-α (left) or rHsTRAIL (0-100 ng/mL; right) on the death of normal (□) and ES-MDS (▦) erythroid precursors cells on culture day 10. Results are mean percentages ± SEM of annexin V (+)/propidium iodide (-) cells compared to untreated cells. (C) Effect of soluble receptor type 1 for TNF-α (TNF-R1:Fc, 0-100 ng/mL; left) and soluble receptor DR4 for TRAIL (DR4:Fc, 0-100 μg/mL; right) on ES-MDS cell viability (n = 5). Results are expressed as optical density (OD) ratios ± SEM between treated and untreated cells in an MTT assay.