Previous data has shown that treatment of Ewing sarcoma cell lines with the reversible non-competitive LSD1-inhibitor SP-2509 resulted in the reversal of the EWS/FLI-driven transcriptional signature, the triggering of unfolded protein response-mediated apoptosis, and led to single agent tumor regression in vivo [3]. This evidence concerns the gene KDM1A and Ewing sarcoma.