# The Proximity of PD-1−CD103+ Tissue-Resident CD8+ T Cells to Tumor Cells Is Correlated with Improved Clinical Outcomes in Patients with Cholangiocarcinoma

## TL;DR

This study shows that the close positioning of specific immune cells near tumor cells in cholangiocarcinoma is linked to better patient outcomes.

## Contribution

The study reveals that the spatial proximity of PD-1−CD103+ CD8+ T cells to tumor cells is a novel prognostic factor in cholangiocarcinoma.

## Key findings

- PD-1−CD103+ CD8+ T cells near tumor cells are associated with improved clinical outcomes.
- These T cells show activation and cytotoxicity gene enrichment compared to exhausted T cells.
- Spatial engagement of these T cells with tumor cells is critical for effective immune surveillance.

## Abstract

Cholangiocarcinoma presents a clinical challenge due to its immunosuppressive tumor microenvironment and therapeutic resistance. This study investigated how the spatial positioning of tissue-resident memory T cells relative to tumor cells is related to anti-tumor immunity and patient survival. We aimed to determine whether the proximity of these immune cells to malignant cells is correlated with patient survival. These findings indicate that the spatial organization of CD8+ tissue-resident memory T cells is a critical prognostic factor, suggesting that effective immune surveillance requires not only the presence of specific T cell subsets but also their precise localization against tumor cells. These insights support the development of immunotherapies that promote effector cell infiltration and engagement within the cholangiocarcinoma tumor microenvironment.

Background/Objectives: Cholangiocarcinoma (CCA) is characterized by a heterogeneous immune microenvironment, where the prognostic significance of CD8+ tissue-resident memory T (TRM) cell activation and spatial positioning remains to be fully elucidated. This study investigated how the activation phenotypes and their spatial distribution relative to tumor cells influence anti-tumor immunosurveillance and predict clinical outcomes in CCA. Methods: Multiplex immunohistochemistry (mIHC) and single-cell RNA sequencing (scRNA-seq) were employed to characterize naïve (PD-1−CD103+CD8+) and exhausted (PD-1+CD103+CD8+) subsets. G-cross function analysis was utilized to quantify the spatial proximity between these specific TRM subsets and tumor cells, correlating the spatial interaction with patient overall survival. Results: scRNA-seq profiling revealed that PD-1−CD103+CD8+ TRM cells were enriched in genes associated with lymphocyte activation and cytotoxicity, while PD-1+CD103+CD8+ TRM cells exhibited an exhaustion signature. Spatially, PD-1−CD103+CD8+ TRM cells exhibited increased interactions with tumor cells, whereas PD-1+CD103+CD8+ TRM cells showed reduced engagement. Therefore, the close proximity of PD-1−CD103+CD8+ TRM cells to tumor cells was identified as a significant predictor of favorable clinical outcomes. Conclusions: The activation state of CD8+ TRM cells combined with their spatial localization constitutes a critical prognostic factor in CCA. Effective anti-tumor immunosurveillance relies on the direct engagement of naïve TRM cells with tumor cells. These findings highlight the potential of PD-1-targeted immunotherapies to remodel the spatial proximity of the tumor microenvironment, potentially promoting the redistribution of effector cells into tumor-proximal regions.