CSIG-20. PROTEOGENOMICS PROFILING REVEALS ENRICHED PROTEIN TRANSLATION REGULATORS AS NEW THERAPEUTIC TARGETS IN DIPG

Abstract

Abstract Diffuse intrinsic pontine glioma (DIPG) is a devastating brain tumor arising in the brainstems of children. Current therapies are ineffective resulting in a median survival rate of less than one year and it is the leading cause of brain tumor-related death in children. A novel mutation in histone H3 protein (H3K27M) was recently identified as a genetic initiation event and affects global K27 trimethylation on histone H3 proteins and DNA methylation. The epigenetic changes caused by H3K27M mutation suggest the existence of an H3K27M-specific transcriptome and proteome. We investigated DIPG tissues at the multi-omics level including total proteome, phosphoproteome, methylproteome and metabolome by mass spectrometry. A total of 30 patient tumours were profiled to identify differentially expressed proteins, differentially phosphorylated proteins, and differentially methylated proteins in tumour tissues compared to normal brains. We identified 2995 proteins that are differentially regulated, suggesting changes in key oncogenic pathways including negative regulation of apoptosis, translation, and metabolic pathways such as methionine salvage and TCA cycle in DIPG. The deregulation of these metabolic pathways due to the differentially expressed proteins in DIPG cells was confirmed by metabolomics studies. Protein phosphorylation and protein methylation profiling of DIPG implicated that translation-related proteins were the most highly modified (post-translationally) proteins in DIPG tissues. Furthermore, protein translation measured by CyTOF showed higher translation rates in DIPG and immortalized astrocytes carrying H3K27M than their WT counterparts. We investigated the functional consequence of knockdown of the highest methylated translation regulator EEF1A1 and its methyltransferase METTL13. ShRNA knockdown of both, EEF1A and METTL13 in DIPG cells significantly reduced the cell growth. Multi-omics analysis of DIPG highlighted regulation of protein translation as a potential therapeutic target.