GENE-11. LSD1/KDM1A MODULATES AN ONCO-IMMUNOGENIC GENE SIGNATURE IN ADULT GBM AND EPIGENOME-MUTATED PEDIATRIC DIPG

Diffuse intrinsic pontine glioma (DIPG) patients often possess a lysine-to-methionine mutation in histone H3 (H3.1/.3-K27M) that renders them sensitive to perturbations in histone methylation. However, the demethylase KDM1A/LSD1 has not yet been investigated as a therapeutic target in DIPG. Our lab has studied LSD1 in adult GBM, generating RNA-Seq data from LSD1 knockdown cells, for which DAVID pathway analysis was performed with a 1.5-fold change filter. Significantly changed was a set of immune response genes (18 upregulated, 6 downregulated) including stimulatory ligands, antigen presentation and cell motility genes. To validate, LSD1 was knocked down via shRNA in LN18 cells and RT-qPCR performed using unique primers for 13 of the most upregulated immunomodulatory genes. T-tests were significant (p<0.05) for 5/13 of these genes, and one-way ANOVA analysis of all genes was highly significant (p<0.0001) versus scramble control. We further hypothesized that LSD1 chemical inhibitors (LSD1i) could replicate these immunomodulatory gene changes in LN18 cells, as well as in DIPG cells bearing K27M mutations. SLAMF7, 4-1BB, and LCP1 were most significantly changed in LN18 cells across LSD1i treatments via T-test (p<0.05). DIPG cells showed significant data via T-test (p<0.05) for SLAMF7, RAET1E, and MICB. Importantly, ANOVA comparison of data between TCP-treated LN18 and DIPG cells, as well as LN18 LSD1i and LSD1-KD, was not significant (q>0.9999), indicating their induced immunomodulatory gene expression profiles are similar. Interestingly, cytotoxicity of tranylcypromine (TCP), GSK LSD1, and RN-1 was tested, with LN18 significantly more resistant to LSD1i cytotoxicity than DIPG cells, indicating LSD1 may play a key role in DIPG survival. TCP is FDA-approved and the only LSD1 inhibitor known to pass through the blood-brain barrier, which is critical for its use as a potential glioma therapeutic. Ongoing studies are examining if LSD1i can enhance immunotherapeutic efficacy against target cells via our documented gene changes.