Human single cell RNA-sequencing reveals a targetable CD8+ exhausted T cell population that maintains murine low-grade glioma growth

Immune cell infiltration is a common feature of solid cancers, where T cells typically function as cytotoxic effectors to limit tumor growth, prompting therapies that activate this antineoplastic property (immune checkpoint inhibition; ICI). Unfortunately, ICI treatments have been largely ineffective for high-grade brain tumors (gliomas; HGGs). Leveraging several single-cell RNA sequencing datasets, we report greater CD8+ exhausted T cells in human pediatric low-grade gliomas (LGGs) relative to adult and pediatric HGGs. Using several preclinical mouse LGG models (Nf1-OPG mice), we showed that these PD1+/TIGIT+ CD8+ terminally exhausted T cells are restricted to the tumor tissue, where they express paracrine factors necessary for OPG growth. Importantly, ICI treatments with anti-PD1 and anti-TIGIT antibodies attenuate Nf1-OPG tumor proliferation through suppression of cytokine-mediated immune axis support, rather than by T cell-mediated cytotoxicity. Collectively, these findings establish a previously unrecognized function for CD8+ exhausted T cells as specialized regulators of LGG maintenance.