BIOM-13. THE MIR-17/92 CO-EXPRESSED NETWORK IS ENRICHED IN AGGRESSIVE PEDIATRIC BRAIN TUMORS

Abstract

Abstract BACKGROUND Over the past two decades, the understanding of miRNA biology has drastically increased as miRNAs have been found to pervade most aspects of molecular biology–from cellular growth to apoptosis. Nevertheless, there has been little understanding of the role of miRNAs in pediatric brain tumors. In this study, we sought to correlate miRNA expression with pediatric brain tumor histologies. METHODS Weighted gene co-expression network analysis (WGCNA) was performed to determine co-expressed miRNA networks that correlated with distinct brain tumor histologies. Our study cohort consisted of miRNA-sequencing of 262 pediatric brain tumor histologies consisting of Atypical Teratoid/Rhabdoid tumors, Craniopharyngioma, Ependymomas, Ganglioglioma, Low-grade astrocytic tumors, High-grade astrocytic tumors, and Medulloblastoma. We utilized associated multi-omics data from the Open Pediatric Brain Tumor Atlas to validate the results. RESULTS WGCNA analysis revealed a distinct miRNA network consisting of 32 miRNAs with miR-17-5p as the hub miRNA that was markedly upregulated in the aggressive brain tumor group (p<0.001). Interestingly, the majority of the miRNA network consisted of the miR-17/92 family of miRNAs, which are known for their oncogenic role in various cancers. To determine the transcriptional regulatory mechanism of miR-17/92 miRNAs, we first looked at sample-matched RNA-sequencing data. The gene encoding for the miR-17/92 miRNAs, MIR17HG, was significantly overexpressed (p<0.001). Further upstream, we observed that E2F1/2/3, known transcriptional regulators of MIR17HG, gene and protein expressions were significantly overexpressed (p<0.01). Sample-matched phospho-proteomics data indicated the E2F regulator, RB1, being hyperphosphorylated–additionally supporting the E2F activity in these samples. CONCLUSION These findings reveal a network of oncogenic miRNAs consisting of the miR-17/92 family that are distinctly overexpressed in aggressive pediatric brain tumors. Moreover, we suggest that the E2F-RB1 axis is the upstream regulator of the miR-17/92 family of miRNAs.