PROJECT SUMMARY High grade gliomas (HGG/GBM) across the pediatric, adolescent and young adult (AYA), and adult populations represent a common unmet therapeutic need underpinned by the cellular heterogeneity of these tumors and its contribution to treatment resistance and residual disease, the ultimate cause of death. Despite numerous molecular studies across this age spectrum, high grade glioma and glioblastoma at recurrence remain poorly characterized, despite being the context for most clinical trials. This project leverages multi-institutional specimen cohorts that addresses the limited availability of paired longitudinal patient specimens and combines such cohorts with state-of-the-art single-cell platforms to profile adult and pediatric gliomas through recurrence. This effort represents a first in kind continuum of research initiative across the pediatric, AYA, adult HGG/GBM landscape with Project HOPE (Pediatric and AYA High-Grade Glioma Omics Project) representing the pediatric/AYA effort, and Project CARE (cellular analysis of resistance and evolution) representing the adult effort. Our central hypothesis is that the interplay between genetic, TME interactions and epigenetic diversity drive cellular plasticity and fuels gliomas adaptation to therapy and intra-tumoral phenotypic heterogeneity. To address this, we will tackle the integration of genetic, epigenetic, and phenotypic heterogeneity across HGG samples, with the following two independent yet interrelated aims: Single cell multi-omic sequencing of cancer cells in pediatric and AYA high-grade gliomas (Aim 1); Single nucleus sequencing of the non-immune microenvironment of pediatric and AYA high-grade gliomas (Aim 2).