ETS-, ERG-, and FLI-1–immortalized cells express CD41 and c-kit and show enhanced STAT-3 phosphorylation. (A) Comparison of CD41 and c-kit expression in ETS2-, ERG-, and FLI-1–overexpressing Gata1-knockdown fetal liver hematopoietic cells isolated from methylcellulose after 4 weeks of culture. Plots are representative of 3 independent experiments. Significance levels for differences for ERG and FLI-1 in comparison with MIGR1 are for CD41 expression (singly positive) only: ERG (P < .01), FLI-1 (P < .04); for CD41/c-kit double-positive gate: ERG (P < .02); c-kit expression: ERG (P < .008), FLI-1 (P < .03). (B,C) Comparison of phospho-STAT3 and phospho-STAT5(a/b) staining of fourth-generation ETS2-, ERG-, and FLI-1-overexpressing Gata1-knockdown fetal liver hematopoietic cells. Significance levels for differences in phospho-STAT3 signaling in comparison with MIGR1: ERG (P < .01), FLI-1 (P < .009), and ETS2 (not significant). P values were calculated by comparing the percentage of cells stained for phospho-STAT3 in the different groups for 3 independent experiments.