LSD1 inhibition with GSK-LSD1 is PU.1 dependent. (A) In vitro IC₅₀ growth curve of PU.1 URE WT, heterozygous (het), and KO MLL-AF9 leukemia cells treated with increasing concentrations of GSK-LSD1. n = 3. (B) Colony-formation assay performed by plating 500 GFP⁺ cells derived from primary MLL-AF9 PU.1 URE WT, heterozygous, or KO leukemic mice with or without GSK-LSD1. n = 3. (C) Representative 1° colony-forming unit (CFU) assay colonies showing persistence of more immature colonies in PU.1 URE het and KO cells. Bar, 0.1 mm. n = 3. (D) Representation of morphologies derived from 1° CFU and 2° CFU assays upon GSK-LSD1 treatment (c, control; G, granulocyte; GM, granulocyte/macrophage; L, LSD1i; M, macrophage). n = 3. (E) Cytospins of cells isolated from PU.1 URE heterozygous and KO 1° CFU assays. Scale bar, 10 µm. (F) Kaplan-Meier survival curves of PU.1 URE WT (left), PU.1 URE heterozygous (middle), and PU.1 URE KO (right) secondary transplanted mice treated with vehicle or GSK-LSD1 for 2 weeks. n = 5 mice per cohort. CFC, colony-forming cell.