CD4 memory T cells orchestrate therapy-responsive immune niches in colorectal cancer liver metastases

Keywords

• Colorectal cancer liver metastasis

• T cell-driven cancer immunity

• Immune niches

Main Findings

Colorectal cancer (CRC) is the fourth leading cause of cancer-related mortality worldwide. Approximately 50% of patients develop liver metastases, making it the most frequent site of distant organ metastasis. Current treatment strategies include surgical resection and systemic chemotherapy; however, surgical intervention is feasible in only 10–20% of cases, and the associated 5-year survival rate remains as low as 30%.

In this preprint, the authors characterize the immune architecture of colorectal liver metastases using high-dimensional flow cytometry on 76 region-matched samples do define lymphoid compartments and used a single cell omics platform, BD Rhapsody scRNA‑seq with AbSeq and paired TCR on T cells to characterize CD4 Mem1, Mem 2 and CD8 differentiation-exhaustion states. Memory and regulatory CD4 T cells are enriched within tumor cores, whereas cytotoxic effector cells are largely excluded. Patients who responded to neoadjuvant chemotherapy exhibited a distinct immune profile marked by Th1-like CD4 memory T cells (Mem2) and stem-like/effector memory CD8 T cells. In contrast, non-responders were characterized by the predominance of an alternative CD4 memory subset (Mem1) and regulatory T cells.

Functional experiments suggested a clear division of labor between T cell subsets. CD4 Mem2 cells primarily acted as helper cells, signalling through CD40L and cytokine pathways, whereas CD8 effector memory T cells were responsible for direct tumor cell killing. Spatial analyses showed that patients who responded to therapy formed well-organized “therapy-responsive immune niches” (TRINs), where CD4 T cells, CD8 T cells, and antigen-presenting cells were found clustered together, especially at the invasive margin and within the tumor core.

Limitations & Suggestions

While we acknowledge the effort to curate this data in an exclusively human setup, there are some experimental and technical suggestions that could improve the conclusions drawn from this work:

• The patient cohort is very heterogenous, particularly with respect to treatment. Patients received a range of neoadjuvant chemotherapy regimens, sometimes in combination with targeted therapies and patients with different treatments were used in between the experiments (e.g. single-cell Rhapsody profiling was performed on only eight patients, of whom just two were classified as partial responders, while the remaining six were non-responders (TRG ≥3), excluding the responders from the screening). Patient material is understandably limited, but grouping patients by treatment regimen or response status for specific analyses would strengthen the conclusions, and key experiments could be replicated in a more homogeneous neoadjuvant-treated cohort.

• The study does not include data from the corresponding primary colonic tumors, leaving open the question of how primary tumor features may shape the immune landscape of liver metastases.

• Although the study identifies strong associations between CD4 Mem2 and CD8, it stops short of demonstrating a role for these cells in tumor regression. The ex vivo stimulation assays confirm that these cells are functionally competent, as shown by cytokine production and activation marker expression, but they do not directly assess anti-tumor activity. Additional functional experiments, such as co-culture assays with autologous tumor cells or patient-derived organoids, could be done to determine whether CD4 Mem2 cells actively support CD8-mediated tumor killing and whether this interaction leads to meaningful tumor cell elimination.

• The analysis focuses primarily on lymphoid populations, while the myeloid compartment, despite representing a substantial portion of the tumor immune infiltrate, is less thoroughly characterized. Given that the proposed mechanism centers on interactions between T cells and antigen-presenting cells, more detailed profiling of myeloid populations would help clarify which specific subsets support productive anti-tumor immunity within therapy-responsive immune niches. For example, high-dimensional myeloid-focused flow could be used to understand DC and macrophage states (maturation, cytokine and costimulatory profiles), and multiplex imaging or spatial transcriptomics could then link these phenotypes to TRINs in situ. Functionally, ex vivo co-culture assays of sorted TRIN-associated DC/macrophage subsets with autologous CD4/CD8 T cells, measuring antigen presentation, costimulation, and T-cell cytokine/effector readouts, would provide evidence that the identified APC populations are indeed licensing and sustaining anti-tumor T-cell responses within these niches.

Significance/Novelty

This study shifts attention away from the traditional emphasis on CD8 cytotoxic T cells and highlights a central role for CD4 T cells (particularly Th1-like memory populations) in shaping responses to chemotherapy in microsatellite-stable colorectal liver metastases, a disease long viewed as immunologically “cold”. By identifying TRINs as key spatial structures in tumors, this work suggests that the spatial organization of immune cells within the tumor microenvironment is more important than their overall abundance. These findings add to the growing recognition that CD4 helper T cells act as key coordinators of anti-tumor immune responses and offer a concrete example of how spatial immune architecture could influence treatment outcomes. From a clinical perspective, especially for patients with MSS colorectal cancer who currently see little benefit from checkpoint blockade, the immune signatures described here could help predict which patients are more likely to respond to therapy.

Credit

Reviewed by Maria Naumova and Öykü Elaslan as part of a cross-institutional journal club between the Max-Delbrück Center Berlin, the Ragon Institute Boston (Mass General, MIT, Harvard), the University of Virginia, the Medical University of Vienna and other life science institutes in Vienna.

The author declares no conflict of interests in relation to their involvement in the review.