Abstract
Pediatric midline gliomas, mainly DIPGs, are a rare and deadly cancer of early childhood, with a 9-month median survival post-diagnosis and a 2-year survival rate of <10%. Their growth on the brainstem makes surgical resection impossible and radiation provides only temporary survival benefit. Epigenetic therapies have shown pre-clinical promise in patient-derived DIPG models, however the H3K4 demethylase LSD1 remains an unexplored target in this disease. Treatment with LSD1 inhibitors (LSD1i) tranylcypromine (IC50: ~1.5mM), GSK LSD1 (IC50: ~400uM), RN-1 (IC50: ~60uM), and Seclidemstat (SP-2577) (IC50: ~13uM) is cytotoxic to DIPG cells, with GSK LSD1 and SP-2577 displaying the least toxicity to normal human astrocytes. As epigenetic therapeutics also change a cell’s transcriptome, we mined our previously published RNA-Seq data from adult GBM cells and identified an immunogenic gene signature controlled by LSD1. Knockdown of LSD1 and sub-cytotoxic LSD1i treatment generates a conserved upregulation of immunogenic receptors including SLAMF7, MICB, ULBP4, and 4-1BB. In a dataset of 235 pediatric high-grade gliomas, expression of our gene signature inversely correlates with LSD1 expression (p<0.0001, unpaired T-test), consistent with our data using LSD1 inhibitor treatment. These ligands regulate the innate immune response, and indeed LSD1i pre-treatment enhances NK cell cytotoxicity against DIPG. Murine models of DIPG created from Nestin-driven deletion of TP53 display LSD1i sensitivity similar to human cells, regardless of H3.3 mutational status (WT v. K27M). Our findings support that LSD1 can be targeted in DIPG for both direct cytotoxicity and as a transcriptional repressor in combination with immunotherapy regimens.