This study exploited a syngeneic hypermutated high-grade glioma model that shows a dichotomous response to combined PD-1 and CTLA-4 blockade. The primary objective was to identify tumor-infiltrating T-cell populations and clonal behaviors that distinguish ICI-responsive from non-responsive tumors, and to validate those findings in human high-grade glioma tissue following neoadjuvant anti–PD-1 therapy.
Tumor-infiltrating T cells from responding and non-responding tumors were analyzed using single-cell RNA sequencing coupled with T-cell receptor sequencing. This combined approach allowed the authors to define transcriptional phenotypes of intratumoral T cells, map clonal expansions, and associate functional transcriptional programs with tumor-reactive TCR clonotypes. The authors also functionally validated tumor-reactive clonotypes, although detailed methods and exact validation metrics are those reported in the source primary text.
A distinguishing feature of ICI response in this model was intratumoral clonal expansion of tumor-reactive cytotoxic T cells. Responding tumors contained clonally expanded cytotoxic T-cell populations that were transcriptionally versatile, suggesting these expanded cytotoxic clones actively participate in anti-tumor activity following combined checkpoint blockade.
ICI response also associated with increased infiltration of CXCR6+ CD4+ tissue-resident memory (Trm) cells. These CD4+ Trm were enriched in responsive tumors, implicating this population as a marker — and potential mediator — of successful checkpoint inhibitor therapy in the hypermutated glioma model. The authors highlight CXCR6 expression as a distinguishing feature of these intratumoral CD4+ cells.
The study identified CD4+ stem-like memory T cells in responding tumors that displayed elevated interferon-response gene programs. Trajectory analyses indicated that, in responders, these stem-like CD4+ cells progress toward clonally expanded Trm phenotypes. In contrast, in non-responding tumors, trajectories favored differentiation toward exhaustion. This divergence suggests that the fate of stem-like CD4+ populations — toward functional residency versus exhaustion — is a key determinant of ICI outcome in this model.
In responsive tumors, CD4+ Trm engaged in cellular interactions with infiltrating CXCR3+ tumor-reactive and clonally expanded cytotoxic T cells. The cytotoxic T cells in this context were described as transcriptionally versatile despite clonal expansion, and the presence of CD4+ Trm coincided with this active cytotoxic compartment. The data support a model in which CD4+ tissue residency may sustain or coordinate effector cytotoxic responses after checkpoint blockade.
To assess clinical relevance, the authors interrogated a dataset of IDH1 wildtype glioblastoma patient tissue obtained after neoadjuvant pembrolizumab. In this human dataset they observed increased CXCR6 expression in CD4+ T cells and an association between CD4+ Trm presence and prolonged overall survival. These patient-based observations align with the preclinical findings and support the potential translational importance of CD4+ Trm as a biomarker of ICI benefit in IDH1 wildtype high-grade glioma.
The authors conclude that CD4+ tissue-resident memory T cells, marked by CXCR6, are determinants of response to combined checkpoint inhibition in their hypermutated glioma model and are associated with improved outcomes in IDH1 wildtype glioblastoma patients treated with neoadjuvant anti–PD-1 therapy. They propose that CD4+ Trm warrant further investigation to improve immunotherapy outcomes in high-grade glioma.
This report is a preprint and has not undergone peer review. The source declares competing interests for some authors and lists funding from the German Research Foundation. Specific numerical metrics, cohort sizes, statistical values, and detailed experimental protocols beyond what is summarized here are present in the full preprint text and supplementary materials; if those details are needed they should be consulted directly in the source document.