The proteomic landscape of diffuse midline glioma highlights the therapeutic potential of non-histone protein methyltransferases.

Background: Diffuse midline glioma (DMG) is a highly aggressive pediatric brain tumor with limited treatment options despite extensive genomic characterization. The aim of this study was to investigate the proteomic landscape of DMG to identify potential therapeutic targets.

Methods: We conducted a comprehensive proteomic analysis using LC-MS3, along with DNA methylation and DNA/RNA sequencing in 55 DMG patients' samples. post-translational modification profiling (phosphoproteome and methylproteome) was conducted in 30 patient samples. We then investigated the effects of modulating key protein targets on protein methylation, protein synthesis, and DMG cell growth in vitro and in vivo.

Results: DMGs exhibited high global protein methylation, with significant enrichment of translation machinery proteins and factors involved in apoptosis regulation. Surprisingly, while targets of key kinases were highly phosphorylated, overall protein phosphorylation was lower in DMG compared to normal brain tissues. Non-histone methyltransferases METTL13 and METTL21B, along with protein kinases PAK2, PRKACA, and AKT1, were identified as key players in DMG methylproteome and phosphoproteome, respectively. METTL13 knockdown led to reduced EEF1A1 protein methylation, a shift in oncoprotein synthesis, and inhibited DMG cell growth in vitro and in vivo.

Conclusions: Our findings highlight the dependency of DMG on methyl-signaling pathways, particularly involving METTL13, which regulates EEF1A1 protein methylation and oncoprotein synthesis. Targeting the non-histone methyltransferases offers a promising therapeutic strategy for DMG. This study underscores the potential of post-translational modifications, specifically methyl-signaling pathways, as novel therapeutic targets for DMG and possibly other currently incurable cancers.