(A) Percentage of cell viability, as measured by CellTiterGlo, of SU-DIPG13 treated with 10 µM Sulfopin or with combined treatment of 10 µM Sulfopin and the indicated agent (putative targets left to right: JMJD3, MLL1, EZH2, histone deacetylases [HDAC]), compared to DMSO. For Sulfopin and Vorinostat mean±SE of at least two independent experiments is shown. For all the other drugs mean ± SD of three technical replicates is shown. In the combination of Sulfopin and Vorinostat, only ~20% of cells survive the treatment. ***p<0.001 (two-sample t-test). (B) Cell viability, as measured by CellTiterGlo, of eight diffuse midline glioma (DMG) cultures (SU-DIPG13, SU-DIPG6, SU-DIPG17, SU-DIPG25, SU-DIPG50, SU-DIPG36, SU-DIPG38, and SU-DIPG21), treated with the indicated concentrations of Vorinostat for 3 days, compared to DMSO. Mean ± SD of two technical replicates is shown. Logarithmic scale is used for the x-axis. (C) Percentage of cell viability, as measured by CellTiterGlo, of seven DMG cultures (SU-DIPG6, SU-DIPG17, SU-DIPG25, SU-DIPG50, SU-DIPG36, SU-DIPG38, and SU-DIPG21), treated with Sulfopin and Vorinostat at the indicated concentrations, compared to DMSO. (D) Cell viability as measured by CellTiterGlo, of SU-DIPG13 and SU-DIPG6-GFP cells treated as indicated, relative to DMSO. Mean ± SE of two independent experiments is shown. (E) BLISS index for each concentration of Sulfopin and Vorinostat, in the eight DMG cultures indicated in C. Synergy: Bliss < 1,Additive: Bliss = 1, Antagonist: Bliss > 1. Additive effect was detected in the majority of the drug doses of the H3.3-K27M DMG cells, and in the higher dosages of Vorinostat in the H3.1-K27M cells. (F) Cell viability as measured by CellTiterGlo, of eight DMG cultures treated with Sulfopin (0 µM, 2.5 µM, 5 µM, 10 µM, 20 µM, and 40 µM) and Vorinostat (0.33 µM), compared to DMSO. H3.3-K27M and H3.1-K27M cultures are indicated in blue and orange, respectively. Mean ± SD of two technical replicates is shown. H3.3-K27M cells showed higher sensitivity to the combined treatment compared to H3.1-K27M cells. (G–H) RT-qPCR analysis of MYC, and its target genes NOC4L and PSMD3, in eight DMG cultures. Mean ± SD of two technical repeats is shown. H3.3-K27M cells show higher expression compared to the H3.1-K27M cells. ***p<0.001 (two-sample t-test). (I) Normalized expression levels of the indicated MYC target genes in SU-DIPG13 cells treated as described in Figure 2G. Mean ± SD of three technical repeats is shown. The expression of these genes is reduced following the combined treatment. **p<0.01, ***p<0.001 (two-sample t-test). (J) RNA sequencing was performed on SU-DIPG13 treated with either Sulfopin (10 µM, 8 days), Vorinostat (1 µM, 72 hr) or Sulfopin+Vorinosat (10 µM, 8 days and 1 µM, 72 hr), compared to DMSO. Principal component analysis (PCA) of all genes detected by RNA-seq is shown. Three technical repeats are shown. (K) Table presenting the total numbers of significantly differentially expressed genes in each treatment compared to DMSO (adjusted p-value≤0.05, |log2FoldChange|≥1, and baseMean≥5). (L) Volcano plots presenting all genes detected in each treatment compared to DMSO. Significantly differentially expressed genes are colored. (M) Heatmap presenting selected genes from cluster 1 (as shown in Figure 2B) that were downregulated in the combined treatment compared to DMSO. Color intensity corresponds to the standardized expression, low (blue) to high (red). Only oncogenes and genes that are involved in glioma progression are shown. (N) Functional enrichment analysis on genes comprising cluster 1 using Enrichr (Kuleshov et al., 2016) algorithm comparing to the Molecular Signatures Database (MSigDB) hallmark gene set collection (Liberzon et al., 2015). Dashed line denotes adjusted p-value=0.05. mTORC1 signaling is highly enriched among cluster 1 genes. (O) Gene set enrichment analysis (GSEA) on SU-DIPG13 treated with combination of 10 µM Sulfopin and 1 µM Vorinostat compared to DMSO, showing significant downregulation of the mTOR oncogenic signature (MTOR_UP.N4.V1_UP; MSigDB C6 Oncogenic Signature; Wei et al., 2006), and the IL-6/JAK/STAT3 signaling pathway (HALLMARK_IL6_JAK_STAT3_SIGNALING; MSigDB hallmark gene set collection; Liberzon et al., 2015), in the combined treatment. NES: normalized enrichment score. FDR: false discovery rate. (P) RT-qPCR analysis of mTOR gene in SU-DIPG6 cells (left) and SU-DIPG13 (right), treated as indicated in Figure 2G. Mean ± SD of two technical repeats is shown. The expression of mTOR is reduced following the combined treatment. (Q) mTOR expression and BLISS index measured in eight DMG cultures. Pearson correlation coefficient (r) is indicated. Gray area depicts 95% confidence interval for regression line. Negative correlation was detected between the two measures.