CSIG-31. MULTI-OMICS TO EDGE INTO PRECISION MEDICINE FOR DIPG

Abstract

Abstract DIPG is an incurable pediatric brain tumor with 80% of patients harboring H3F3A (H3.3) mutation that substitutes methionine for lysine at position 27 (K27M), resulting in global depletion of H3.3K27 me3 (trimethylation). These histone mutations modify the epigenome and alter oncogenic transcription, causing oncogenic insults to progenitor cells in early neurodevelopment (1). To determine the reprogramming pathways in the cell context of H3.3K27M tumors, we conducted LC-MS based proteomic and phosphoproteomic analysis on seven patient-derived DIPG cell lines. Three normal neuronal stem cell lines were included as non-tumor brain cells for comparison. Pathway analysis identified 29 pathways that are significantly altered in DIPG compared to normal brain cells at both the protein abundance and phosphosite level. Notably, AKT and MAPK associated PI3K signaling, VEGF signaling, mTOR signaling, and HIF1a signaling were differentially active in H3.3K27M tumors compared to healthy control cell lines. We saw significantly higher activity of multiple kinases involved in axon guidance and cytoskeletal remodeling in DIPG, such as PTK2B, DYRK2, TTBK2 and MARK2. This is the first time to report an increased abundance and kinase activity of PYK2 protein (coded by PTK2B), a close homologue of FAK and its associated signaling in DIPG. PYK2 has been proposed to act in concert with Src to link Gi- or Gq-coupled receptors with the mitogen-activated protein (MAP) kinase signaling pathway (2). Because of the shared signaling across kinase pathways, targeting activated PYK2 in DIPG may complement inhibitors of other dysregulated signaling networks in DIPG such as MAPK2, VEGFR, PI3K and Src. Our data also found that IL13RA2 was upregulated in DIPG. We conclude that for H3 K27M DIPG tumors, campaigns to target PYK2, MAPK2, VEGFR, PI3K, Src and IL13Ra2 using small molecules that traverse the blood brain barrier loom as promising opportunities for drug development.