Published on November 05, 2026
Abundant CD8+ Tumor-Infiltrating Lymphocytes in Glioblastoma Harbor Distinct Exhaustion Signatures in Potentially Reactive Subsets
by Alex Kadhim
Exhausted T cells have often been reported as absent from glioblastoma (GBM), yet in the minority of tumors that are densely infiltrated they are plainly present, clonally expanded, and marked by LAG3. These findings, published in the British Journal of Cancer come from authors at the Aichi Cancer Center Research Institute using surgical cohorts from Kyoto Prefectural University of Medicine and Okayama University. The study identifies tumors rich in tumor-infiltrating lymphocytes (TILs) as the realistic starting point for antigen-specific immunotherapy.
GBM has a median overall survival near 14.6 months, and immunotherapy has been constrained there by low tumor mutational burden, an immunosuppressive microenvironment, and scarce TILs. Single-cell studies had reported antigen-specific T cells to be absent from GBM while flow cytometry showed a prominent exhausted phenotype, a contradiction the authors set out to resolve. Tumors from 56 patients with newly diagnosed isocitrate dehydrogenase (IDH)-wildtype GBM were profiled by bulk RNA sequencing (n = 44), flow cytometry (n = 21), and T cell receptor (TCR) repertoire reconstruction. Two TIL-rich cases were sorted for paired single-cell RNA and TCR sequencing and integrated with public GBM datasets and lung cancer samples carrying validated antigen-specific TCRs, with reactive clones nominated by the classifier predicTCR.
TIL-rich tumors accounted for 9.1% of the Aichi cohort, 8.5% of TCGA-GBM, and 7.5% of GLASS-GBM. The two sorted cases yielded 15,418 CD8⁺ T cells in nine clusters, four carrying exhaustion markers led by LAG3. Across 44,037 integrated CD8⁺ T cells, LAG3 and CXCL13 were numerically higher in the Aichi samples without sample-level significance (p = 0.140 and p = 0.136) yet significantly elevated within exhaustion-enriched clusters, and the Tirosh exhaustion score was higher overall (p = 0.029). These samples also held more expanded clonotypes (p = 0.030), with the high-clonality group enriched for LAG3, NKG7, GZMK, and CCL4L2. Against lung cancer data, GBM exhausted cells grouped with validated antigen-specific T cells, and predicTCR correctly classified 5 of 10 such TCRs, although none of 61 predicted neoantigen peptides elicited a response. Exhausted, clonally expanded TILs therefore do exist in a measurable minority of glioblastomas, and those patients, rather than the TIL-poor majority, are where antigen-specific and LAG-3-directed strategies should be tested first.
Reference
Okamoto T, Mizuta R, Demachi-Okamura A, et al. Abundant CD8⁺ tumor-infiltrating lymphocytes in glioblastoma harbor distinct exhaustion signatures in potentially reactive subsets. Br J Cancer. 2026. https:doi.org/10.1038/s41416-026-03619-3
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