Immunotherapy for Glioblastoma by Targeting an Immunoregulatory Neuropeptide - lioblastoma (GBM) is the most lethal primary brain tumor, marked by limited treatment options and poor survival. GBM is also remarkably resistant to immunotherapy due to CD8⁺ T cell exclusion and dysfunction, largely driven by immunosuppressive myeloid cells—particularly tumor-associated macrophages (TAMs). This positions TAMs as central targets for rewiring anti-tumor immunity. Our studies uncover a previously unrecognized tumor–host interaction: GBM activates trigeminal sensory neurons—specifically, meningeal nociceptors—which in turn release elevated levels of the immunoregulatory neuropeptide calcitonin gene– related peptide (CGRP). CGRP acts via its receptor, receptor activity–modifying protein 1 (RAMP1), to reprogram TAMs toward an immunosuppressive phenotype. In syngeneic orthotopic murine GBM models, nociceptor ablation significantly prolongs survival and, importantly, sensitizes previously unresponsive GBM to immune checkpoint blockade (ICB). It enhances antitumor immunity by reducing TAM-mediated suppression, boosting CD8⁺ T cell infiltration and function, and limiting T cell exhaustion—a hypofunctional state characterized by impaired cytokine production, reduced cytotoxicity, and sustained expression of inhibitory receptors. Strikingly, GBM-bearing mice with myeloid-specific RAMP1 deletion phenocopy these effects. Furthermore, the survival benefit is lost upon CD8⁺ T cell depletion, underscoring a critical CGRP-driven TAM–T cell axis in immune escape. At the molecular level, we uncover a mutually antagonistic interaction between CGRP and interferongamma (IFN-γ), a key pro-inflammatory cytokine essential for anti-tumor immunity. CGRP suppresses IFN-γ– STAT1 signaling in TAMs, while IFN-γ inhibits CGRP-induced cAMP signaling and RAMP1 expression— establishing a reciprocal regulatory loop that governs TAM polarization. Of note, while TAMs are known drivers of immune suppression in GBM, the upstream signals that program their identity remain largely unclear. We identify a neuroimmune axis in which nociceptor-derived CGRP reprograms TAMs to drive CD8⁺ T cell exhaustion in the GBM TME. However, how CGRP reprograms TAMs at the molecular level—and how this drives T cell exhaustion—remains unresolved. Addressing this will define a new mechanism of immune suppression in GBM and reveal actionable neuroimmune targets to overcome immunotherapy resistance. In this proposal, we will define how CGRP–RAMP1 signaling enforces TAM-mediated immune suppression by dampening TAM sensitivity to IFN-γ. We will dissect the transcriptional and epigenetic programs underlying this crosstalk using single-cell multiomic profiling, and leverage spatial transcriptomics and advanced imaging to map how RAMP1⁺ TAMs promote CD8⁺ T cell exhaustion within the GBM TME. Because these studies aim to resolve integrated neuroimmune interactions that require intact tumor architecture, immune competence, and neuronal circuitry, we will employ immunocompetent, syngeneic orthotopic murine GBM models, which are essential to faithfully recapitulate these processes in vivo and cannot be modeled in vitro. By identifying the CGRP–RAMP1 axis as a targetable neuroimmune checkpoint, this work reveals a previously uncharacterized driver of immune evasion in GBM and opens the door to repurposing FDA-approved drugs targeting trigeminal sensory neurons and their downstream signaling pathways to overcome immunotherapy resistance in this intractable cancer
