ST-SEQ Mapping Unveils TME Heterogeneity in Angioimmunoblastic T-Cell Lymphoma

Research utilizing spatial transcriptome sequencing (ST-SEQ) has identified distinct tumor microenvironmental (TME) subtypes in angioimmunoblastic T-cell lymphoma (AITL), offering a potential breakthrough in patient stratification and targeted immunotherapy strategies.¹

AITL represents the second most common subtype of peripheral T-cell lymphoma (PTCL) and remains a clinical challenge characterized by an aggressive course and exacerbated systemic inflammation. Current outcomes remain suboptimal, with a 5-year overall survival (OS) rate of less than 40%.²

While neoplastic cells in AITL are known to arise from the monoclonal expansion of follicular helper T cells (TFH)—typically expressing markers such as CXCL13, CD10, BCL6, PD-1, and ICOS—the complex interplay between these cells and their surrounding microenvironment has remained largely unmapped until now.

Two Distinct TME Profiles

A total of 14 distinct ST clusters were identified across all samples.

Five neoplastic clusters were identified, defined by being predominantly composed of spots from AITL samples (>95%) and high expression of TFH cell markers (CXCL13, MME, BCL6, PDCD1, ICOS). Nine non-neoplastic clusters were also defined, including clusters representing germinal centers, B follicles, T-cell zones, high endothelial venules, the lymph node capsule, and plasma cells.

Analysis of the neoplastic TME revealed features of exacerbated inflammation and immune dysregulation; a significant depletion of naive, activated, memory, and IFN-responsive B cells, indicating a global shift in B-cell phenotypes; and a significant enrichment of M1 macrophages, activated dendritic cells (CCR7+ DCs), and T follicular regulatory cells.

Using ST-SEQ to construct a high-resolution map of the AITL landscape, investigators identified 2 primary neoplastic TME archetypes with divergent molecular drivers and clinical outcomes:

• CD40-CD40LG High (common subtype): The majority of cases fall into this category. This TME is characterized by high CD40-CD40LG activity, reflecting a heavy reliance on germinal center (GC) B cells. This profile is frequently associated with the expression of immune-suppressive genes, potentially facilitating tumor evasion.
• Phagocytosis-Enriched (rare subtype): A previously uncharacterized TME subtype defined by an absence of CD40-CD40LG activity. Instead, this niche is heavily enriched with phagocytosis-associated tumor-associated macrophages (TAMs).

The common TME subtype aligns with previous findings that AITL tumorigenesis is supported by GC B cells via the CD40-CD40LG axis. The uncommon subtype represents a novel discovery, suggesting a different mechanism of tumor support that is independent of this axis and is instead dominated by TAMs.

Clinical Implications and Prognostic Value

To validate these findings, researchers analyzed a 37-patient cohort. The results suggest that TME composition is a primary driver of clinical durability.

Patients identified with the uncommon TME subtype demonstrated significantly longer event-free survival and lower rates of disease relapse.

Trajectory analysis further suggests that these 2 subtypes follow distinct molecular evolutionary paths, implying that a "one-size-fits-all" approach to AITL may overlook critical biological differences that dictate treatment response.

Toward Rational Immunotherapy Design

The discovery of the CD40-CD40LG axis as a dominant feature in the more aggressive TME subtype provides a clear rationale for targeted intervention. Researchers noted that these findings underscore an urgent need for TME-based patient stratification in clinical trials.

By identifying patients based on their specific TME signature, clinicians may eventually be able to guide the rational design of immunotherapies, specifically those targeting the CD40-CD40LG axis or modulating TAM activity in the phagocytosis-enriched subtype.

Study Design and Methodology

The research employed a multi-faceted approach to investigate the AITL TME, integrating genomic and spatial transcriptomic data.

The discovery cohort consisted of tumor samples from 4 patients with AITL and inflamed lymph nodes from 2 noncancerous donors. All patients with AITL were Epstein-Barr virus-positive and received CHOP-like treatment regimens.

The validation cohort included 37 patients with newly diagnosed AITL retrospectively enrolled for immunohistochemistry analysis.

Whole-exome sequencing was used to identify recurrently mutated genes in the 4 discovery cohort AITL samples.

ST-SEQ was performed on frozen tissues from the discovery cohort to profile gene expression while preserving spatial location, generating a total of 16,063 qualified ST spots.

Immunohistochemistry was utilized on the validation cohort to assess the protein expression of key markers (CD68, CD163, CD40LG) for prognostic analysis.

“While validation in an expanded cohort supported our key findings, further characterization of rare AITL TME subtypes will be essential to facilitate precise patient stratification and optimize immunotherapeutic strategies,” concluded Zhang et al, authors of the study.

REFERENCES

1.Zhang X, Sun Y, Wu D et al. Revealing tumor microenvironmental heterogeneity and prognostic value in angioimmunoblastic T-cell lymphoma via spatial transcriptome sequencing. Cell Death Dis 17, 27 (2026). doi: 10.1038/s41419-025-08212-9.

2.de Leval L, Parrens M, Le Bras F, et al. Angioimmunoblastic T-cell lymphoma is the most common T-cell lymphoma in two distinct French information data sets. Haematologica. 2015;100(9):e361-e364. doi:10.3324/haematol.2015.126300