Expression of mutant NE reduces the clonogenic capacity of U937 cells. U937 cells transfected with the indicated NE cDNA were sorted based on GFP expression and plated at limiting dilution in 96-well plates. The number of positive wells on day 14 of culture is shown. Data are normalized to WT-transfected cells, where the number of positive wells was defined as 1. Data represent the mean (± SD) of 3 independent experiments. *P < .05 compared with WT-transfected cells.