PD-1⁺Tim-3⁺CD103⁺ CD8⁺ Tumor-infiltrating Lymphocytes Are Associated With Favorable Outcomes in Colorectal Cancer

Colorectal cancer (CRC) remains the leading cause of cancer-related mortality worldwide and necessitates the development of novel therapeutic strategies. The tumor immune microenvironment (TME) critically influences disease progression and the response to immune checkpoint inhibitors (ICIs). Tumor-infiltrating lymphocytes (TILs) are key components of the TME with established prognostic and predictive significance. Nevertheless, detailed TIL characterization using flow cytometry has not been fully investigated in CRC.

We analyzed TILs from 90 fresh CRC specimens using multicolor flow cytometry to investigate the association between specific T cell subsets and clinical outcomes. Patients were classified into Hot and Cold groups based on hierarchical clustering of TIL marker expression.

The Hot group demonstrated significantly better overall survival (OS) compared to the Cold group (5-year OS: 86.7% vs. 63.9%, p=0.006), although recurrence-free survival (RFS) was not significantly different (5-year RFS: 79.5% vs. 66.1%, p=0.24). CITRUS analysis revealed that PD-1⁺Tim-3⁺CD103⁺CD8⁺ T cells were enriched in hot tumors (32.1% vs. 6.1%, p<0.001) and correlated with a favorable prognosis. Importantly, multivariate analysis demonstrated that a low frequency of PD-1⁺Tim-3⁺CD103⁺ cells among CD8⁺ T cells was an independent prognostic factor for OS [hazard ratio (HR)=3.36, 95% confidence interval (CI)=1.20-9.34, p=0.02].

A high frequency of PD-1⁺Tim-3⁺CD103⁺ CD8⁺ T cells is associated with better survival in CRC, highlighting their potential as a prognostic biomarker and therapeutic target.