LSD1 inhibition with GSK-LSD1 has potent antileukemic activity. (A) GFP chimerism reporting MLL-AF9 allele burden in the bone marrow of GSK-LSD1–treated (red, n = 32) or vehicle-treated (blue, n = 28) leukemic mice following 2 weeks of treatment. (LSD1i = GSK-LSD1). t = 7.833; degrees of freedom (df) = 58. (B) Immunophenotype of GFP⁺ cells from bone marrow of mice after 3 days of vehicle (left) or GSK-LSD1 (right) administration. Double staining with antibodies recognizing Gr1, Mac-1, and c-kit cell surface markers are indicated. n = 3. (C) Kaplan-Meier survival curve of secondary MLL-AF9 leukemic mice. The interval between the dotted lines represents the period of treatment with GSK-LSD1 or vehicle. (D) Kaplan-Meier survival curve of tertiary sublethally irradiated mice transplanted with cells obtained from secondary mice treated with either vehicle (blue) or GSK-LSD1 (red) for 3 days. (E) Wright-Giemsa–stained cytospins of AML cells cultured after a 48-hour exposure to 0.5 µM GSK-LSD1. Scale bars, 10 µm. (F) Histogram plots demonstrating increased cell surface expression of CD86 after treatment of murine MLL-AF9 leukemia cells with 0.5 μM GSK-LSD1 (red) relative to vehicle control treatment (black). (G) Graph representing cell cycle states of murine AML cells treated with 0.5 µM GSK-LSD1 for 48 hours. n = 3; subG0/G1: t=4.49, df=6; G0/G1: P = .186 n.s.; S: t=14.9, df=6; G2/M: P = .776. (H) Chimerism of human CD45⁺ AML derived cells from bone marrow of PDX mice treated for 6 weeks with vehicle (blue) or GSK-LSD1 (red) at a dose of 0.5 mg/kg. n = 5. (I) Total cellularity of hCD45⁺ and hCD45⁺/hCD33⁺ cells derived from bone marrow of PDX mice treated with vehicle or GSK-LSD1 (0.5 mg/kg). PDX recipient mice were transplanted with cells from bone marrow of an AML patient harboring the MLL-AF9 gene rearrangement. n = 5. (J) Bar graphs representing the proportion of hCD45⁺ engrafted PDX cells expressing hCD11b or hCD86 after treatment with vehicle or GSK-LSD1. n = 5. (K) Morphology of Wright-Giemsa–stained hCD45⁺ bone marrow cells derived from PDX NSG mice treated with vehicle or GSK-LSD1. Bar, 10 µm. n = 3. APC, allophycocyanin; BM, bone marrow; ctrl, control; DMSO, dimethyl sulfoxide; PE, phycoerythrin.