Extracellular glutamate drives glioblastoma invasion through NMDA receptor signaling in a three-dimensional engineered biomaterial platform

Glioblastoma (GBM) tumors are characterized by an excess of extracellular glutamate, one important source of which is the tumor cells themselves. This abundance of glutamate promotes GBM proliferation, migration, and therapeutic resistance, and causes excitotoxicity in nearby neurons. However, despite glutamate’s clear role in promoting GBM aggression, the exact mechanisms through which excess glutamate drives these phenotypes, particularly 3D invasion, remain incompletely understood. To address this gap, we used a 3D brain-mimetic hyaluronic acid (HA) hydrogel to investigate the role of glutamate signaling in GBM 3D invasion. We demonstrate that inhibiting the glutamate N-methyl-D-aspartate receptor (NMDAR) reduces invasion from 3D tumorspheres, a result that is reproducible across multiple continuous culture models and a patient-derived xenograft cell line. We then conduct glutamate-driven invasion studies in 3D HA-based devices that can be micro-dissected to isolate and differentially analyze invasive and non-invasive cells. Transcriptomic analysis of invasive, non-invasive, and drug-treated populations of cells reveals that NMDAR inhibition suppresses several pathways associated with invasion-relevant processes, including matrix remodeling and collagen deposition. Our work speaks to the potential value of biomaterial platforms for identifying the autocrine and paracrine mechanisms through which neurotransmitters fuel GBM invasion.