Features and Therapeutic Potential of T-Cell Receptors in High-Grade Glioma
High-grade gliomas (HGGs), particularly glioblastoma (GBM), represent some of the most aggressive and lethal primary brain tumors, with a median survival of 14.6 months and a 5-year survival rate below 6%. Conventional treatments, including surgery, radiotherapy, and chemotherapy, offer limited efficacy. Emerging immunotherapies, particularly those targeting T-cell receptors (TCRs), hold promise for improving outcomes. This study explores the diversity and functional characteristics of TCR repertoires in HGG patients, identifying potential therapeutic TCR sequences associated with prolonged survival.
Introduction
HGGs are characterized by rapid progression, resistance to therapy, and high mortality. Despite advances in standard treatments, recurrence is nearly inevitable, underscoring the need for novel therapeutic strategies. Recent studies highlight the role of T-cell-mediated immunity in tumor control, with TCR-engineered T-cell (TCR-T) therapy emerging as a promising approach. TCRs, particularly their beta chains (TRB), contain complementarity-determining regions (CDR3) that directly bind antigens, enabling specific recognition of tumor cells. However, the clonality, diversity, and functional relevance of TCR repertoires in HGG remain poorly understood. This study investigates TCR repertoire features in HGG patients, focusing on their association with survival and therapeutic potential.
Methods
Study Cohort and Sample Collection
Between 2011 and 2018, tumor tissues and blood samples were collected from 35 HGG patients undergoing resection at Beijing Tiantan Hospital and Beijing Shijitan Hospital. Inclusion criteria required no prior radiotherapy or chemotherapy within 20 days pre-surgery. Ten patients provided paired tumor and blood samples, while 25 contributed blood alone. Blood samples from 101 age-matched healthy individuals (19–65 years) served as controls.
DNA Extraction and TCR Sequencing
DNA from tumor tissues and peripheral blood mononuclear cells (PBMCs) was isolated using commercial kits. TCR beta-chain CDR3 regions were amplified via multiplex PCR and subjected to high-throughput sequencing. The immune repertoire (IR) was analyzed using MiXCR software, with a focus on TRB sequences with clonal frequencies ≥10⁻⁵ to exclude systematic errors.
Diversity and Clonality Analysis
TCR diversity was quantified using the Shannon-Wiener diversity index (SHDI). Subsampling (80% of the smallest sample) ensured comparability between groups. SHDI values were calculated as:
[
text{Shannon index} = -sum_{i=1}^{S} left( frac{n_i}{N} ln frac{n_i}{N} right),
]
where ( n_i ) = clone count, ( S ) = unique clonotypes, and ( N ) = total sequences.
Survival and Statistical Analysis
Overall survival (OS) was tracked from surgery until December 2018. Patients were stratified into short-term survival (STS, <16 months) and long-term survival (LTS, ≥16 months). Statistical analyses included t-tests, Mann-Whitney U tests, and Kolmogorov-Smirnov tests using SPSS (v20). Significance was set at ( P leq 0.05 ).
Results
Reduced TCR Diversity in HGG Patients
Blood TCR diversity (SHDI = 7.34) in HGG patients was significantly lower than in healthy controls (SHDI = 8.45; ( P = 0.001 )). Tumor tissues showed even lower diversity (SHDI = 3.48–6.21), reflecting a constrained TCR repertoire in the tumor microenvironment.
Association Between TCR Diversity and Survival
GBM patients surviving ≥16 months (LTS) exhibited higher TCR diversity than STS patients in both blood (( text{SHDI} = 7.44 pm 0.32 ) vs. ( 6.02 pm 0.66 ); ( t = -2.20, P = 0.036 )) and tumor tissue (( text{SHDI} = 6.21 pm 0.33 ) vs. ( 3.48 pm 0.31 ); ( t = -5.49, P = 0.002 )). Enhanced diversity correlated with prolonged survival, suggesting a protective immune response.
TRBV9 as a Protective TCR Region
HGG patients showed elevated TRBV9 and TRBV5 usage in blood compared to controls (9.83% vs. 6.83%, ( P = 0.001 )). In tumor tissues, LTS patients had higher TRBV9 + TRBV4 proportions (7.14% vs. 3.28%, ( t = 3.18, P = 0.019 )), implicating these regions in antitumor immunity.
Identification of a Therapeutic TCR Sequence
Two GBM patients surviving >46 months shared a unique TRB CDR3 sequence (CASSVTSGRSNEQFF) in tumor tissue, accounting for 3.37% of TRB clones in one patient. This sequence, absent in healthy controls and viral-binding TCR databases, suggests tumor-specific recognition. TRBV9 and TRBJ2-1 regions within this sequence highlight its potential for TCR-T therapy.
Discussion
TCR Diversity as a Prognostic Biomarker
The reduced TCR diversity in HGG patients aligns with studies showing T-cell exhaustion in solid tumors. Lower SHDI values in STS patients imply impaired immune surveillance, while higher diversity in LTS patients supports the role of polyclonal T-cell responses in controlling tumor progression.
Functional Relevance of TRBV Regions
TRBV9’s association with prolonged survival may reflect its ability to recognize glioma-associated antigens. TRBV9 and TRBV4 expansion in LTS patients suggests clonal amplification of protective T-cell subsets, consistent with findings in melanoma and lung cancer.
Therapeutic Implications of Tumor-Specific TCRs
The shared TCR sequence in LTS GBM patients represents a candidate for adoptive T-cell therapy. Its tumor specificity, absent in healthy repertoires, minimizes off-target risks. Future studies should validate its antigen specificity and efficacy in preclinical models.
Limitations and Future Directions
The small sample size and retrospective design limit generalizability. Prospective cohorts and single-cell TCR sequencing could refine diversity metrics and elucidate antigen specificity. Incorporating TCR-T therapies targeting TRBV9 into clinical trials may improve HGG outcomes.
Conclusion
This study demonstrates that TCR repertoire diversity correlates with survival in HGG patients, with TRBV9-enriched clones associated with prolonged survival. The identification of a tumor-specific TCR sequence highlights the potential for personalized TCR-T therapies. Enhancing TCR diversity and targeting protective TRB regions may offer new strategies for HGG treatment.
doi.org/10.1097/CM9.0000000000000282
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