LSD1 and the CoREST complex are targeted by UM171. (A) In vitro assay measuring LSD1 enzymatic activity in the presence of 2-PCPA or UM171. Data from 3 to 6 repeats of the assay are represented. (B) Venn diagram showing common target proteins of UM171 between HL-60 and Kasumi-1 cells, identified by TPP. Western blots showing RCOR1 (C) and LSD1, HDAC1, and HDAC2 (D) in UCB CD34⁺ cells treated with 2-PCPA or UM171 for 24 hours. (E) Time kinetics experiment showing RCOR1 and LSD1 protein expression in OCI-AML3 (top panel), HL-60 (middle panel), and U937 (bottom panel) cell lines treated with DMSO or UM171. (F) RCOR1 and LSD1 protein expression in HL-60 cell line treated with UM171 and proteasomal inhibitor bortezomib for 3 hours. (G) Flag-tagged RCOR1-expressing HL-60 cells were treated with DMSO or UM171 for 1.5 hours, and RCOR1 was enriched with Flag IP and analyzed for polyubiquitination. ****P ≤ .0001.