Functional tumor-reactive CD8 + T cells in pancreatic cancer.

BACKGROUND: Traditional methods for detecting tumor-reactive (TR) CD8 + tumor-infiltrating lymphocytes (TILs) in pancreatic cancer usually focus on neo-antigenic epitopes, which is limited by the narrow range of antigenic epitopes, and the lengthy and complex identification processes, resulting in an incomplete understanding of the biological characteristics of TR CD8 + TILs. METHODS: This study introduces a novel approach that integrates single-cell sequencing with deep learning (DL), which enables the identification of tumor-reactive CD8 + T cells without neoantigen screening. The T Cell Receptor Engineered T (TCR-T) cell tumor organoid killing model was employed to validate the functionality of DL-identified TR CD8 + T cells, while spatial transcriptomics was used to confirm receptor-ligand interactions involving TR CD8 + TILs. RESULTS: Comprehensive analyses of TR CD8 + TILs revealed impaired mitochondrial respiratory chain-related pathways regulated by the transcription factor FOS. The TIGIT-NECTIN2 axis was identified as an important immune checkpoint molecule in the tumor microenvironment of pancreatic cancer. T cell receptor (TCR) repertoire analysis demonstrated that some TR CD8 + TILs possess multiple TCR αβ combinations. Furthermore, TCR-T targeting experiments using tumor organoids revealed that combinations of multiple distinct TR TCRs exhibit significantly superior tumor-killing capabilities compared to a single type TCR. Clinically, a higher proportion of TR CD8 + TILs was positively associated with improved responses to neoadjuvant immunotherapy and longer overall survival in pancreatic cancer patients. CONCLUSION: This study represents a significant advancement in the understanding of TR TIL biology and provides a rapid and accurate method to identify TR CD8 TILs.