Inhibition of the NOTCH pathway with dominant negative Mastermind-like 1 decreases proliferation in Rec-1 and SP-49. Cells were transduced in triplicate with a construct expressing dominant negative Mastermind-like 1 (DN-MAML1), which inhibits the transcriptional activity of NOTCH. Proliferation was assessed by incorporation of BrdU that was detected by flow cytometry with an AlexaFluor-647 antibody. To determine the effect of NOTCH inhibition, we compared the difference of proliferation in GFP⁺ and GFP⁻ cells in the DN-MAML1 versus the empty vector (EV) group. *Statistical significance at the .05 level (2-sided t test). Error bars represent SD.