Abstract
To the Editor,
We read with considerable interest the article by Ding et al 1 “Cisplatin and Alternating Temozolomide in Recurrent High-Grade Gliomas: Efficacy and the Role of Tumor-Infiltrating Lymphocytes,” published in Clinical Medicine Insights: Oncology. Their phase 2 trial contributes meaningful data on the feasibility and modest efficacy of a cisplatin-based regimen in recurrent high-grade gliomas, while also sparking complex immunologic questions through its unexpected finding: that lower intratumoral CD8+ T-cell density was associated with improved clinical outcomes.
This counterintuitive observation departs from prevailing oncology paradigms, where robust CD8+ T-cell infiltration typically signals anti-tumor immunity and favorable prognosis across numerous solid tumor types.2,3 The authors’ CGGA-based transcriptomic validation adds further weight, demonstrating improved overall survival in CD8-low gliomas treated with chemotherapy. These data compel a re-examination of what CD8+ infiltration represents in gliomas—particularly within their uniquely immunosuppressive microenvironment.
Gliomas, unlike melanoma or non–small cell lung cancer, are characterized by profound T-cell dysfunction and exclusion, blood-brain barrier constraints, paucity of antigen-presenting cells, and dominant immunoregulatory cell populations such as microglia and M2-polarized macrophages. 4 Within this context, CD8+ infiltration may not equate to effector function. Instead, high CD8+ TIL density may reflect chronic antigen stimulation, T-cell exhaustion, or a reactive, ineffective immune milieu. This notion is supported by the authors’ observation that CD8-high tumors exhibited elevated expression of immune checkpoint molecules, including PDCD1 (PD-1) and CTLA4.
The chemotherapy backbone used in this study—cisplatin and alternating temozolomide—has also been explored previously in patients with recurrent glioma and glioblastoma.5,6 These studies support the tolerability and modest benefit of such regimens, particularly in patients with MGMT-unmethylated tumors. Temozolomide-based schedules have also demonstrated improved pharmacodynamic effects with protracted administration.6,7 From a translational perspective, such regimens may potentiate immunogenic cell death and promote tumor antigen release. This has theoretical implications for sequencing or combining chemotherapy with immune checkpoint inhibitors.
However, the paradoxical CD8-low benefit observed here suggests that immune contexture, not simply cytotoxicity, should inform combination strategies. In fact, CD8-low tumors may represent a more permissive, less immunosuppressed niche—ripe for immune priming—while CD8-high tumors may be more resistant due to T-cell dysfunction.
To further interrogate this biology, we propose that future studies incorporate functional immunoprofiling, including co-expression of LAG-3, TIM-3, and TOX on CD8+ cells, as well as spatial transcriptomic mapping of T-cell location relative to tumor vasculature and myeloid suppressor niches. In particular, the role of glioma-associated macrophages and their crosstalk with CD8+ T cells deserves closer attention.
Importantly, the study’s findings warrant validation in larger, molecularly stratified cohorts. IDH mutation, MGMT methylation, and TERT promoter status are key modifiers of glioma biology and immune phenotype. In addition, steroid exposure, tumor location, and prior lines of therapy must be accounted for as potential confounders in immune correlates.
Moreover, leveraging noninvasive biomarkers such as circulating immune cells, serum cytokines, or even immuno-PET tracers (eg, CD8-targeted radiotracers) could provide dynamic insights into treatment-related immune shifts and help guide rational combination designs. Recent multi-omics approaches, including single-cell RNA sequencing and spatial transcriptomics, have demonstrated their ability to capture immune dynamics in gliomas and should be integrated into future studies.8,9
In conclusion, Ding et al deliver a thoughtful and important contribution by challenging assumptions about CD8+ TILs in glioma. Their data urge a more nuanced, mechanistically grounded interpretation of immune markers in neuro-oncology. We echo their call for continued exploration and believe that such research will be central to unlocking the immunologic vulnerabilities of gliomas.
Footnotes
Acknowledgements
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Consent to participate/Consent for publication
Not applicable. No patient data were used.
Author contributions
SKR and NKR contributed to the conceptualization and original draft preparation. NHP and NL contributed to the writing—review and editing. All authors have read and approved the final version of the manuscript.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Data availability statements
Not applicable. This letter does not report original clinical data.