Identification of a TIGIT-expressing CD8⁺ T cell subset as a potential prognostic biomarker in colorectal cancer

Area of Science:

• Immunology
• Oncology
• Cancer Research

Background:

• TIGIT (T cell immunoreceptor with Ig and ITIM domains) is an inhibitory immune checkpoint receptor implicated in tumor immune evasion.
• Colorectal cancer (CRC) exhibits resistance to current immunotherapies like anti-PD-1, necessitating novel biomarkers for predicting outcomes.
• Identifying reliable immune biomarkers is crucial for stratifying patients and improving therapeutic strategies in CRC.

Purpose of the Study:

• To investigate the role of TIGIT expression as a prognostic biomarker in colorectal cancer (CRC).
• To characterize the TIGIT-expressing immune cell populations within the CRC tumor microenvironment.
• To explore the potential of TIGIT+ immune cells as predictors of therapeutic response in CRC.

Main Methods:

• Analysis of transcriptomic data from CRC patient cohorts to correlate TIGIT expression with survival outcomes.
• Assessment of immune cell infiltration, specifically CD8+ T cells, in relation to TIGIT expression.
• Single-cell RNA sequencing (scRNA-seq) to identify distinct T cell subsets expressing TIGIT, PD-1, and CXCL13.
• In vitro co-culture experiments to elucidate the mechanisms driving T cell phenotype induction by tumor cells.

Main Results:

• Elevated TIGIT expression in CRC was significantly associated with poorer overall survival and disease-free survival.
• TIGIT expression positively correlated with increased infiltration of CD8+ T cells within the tumor microenvironment.
• A unique subset of TIGIT+PD-1+CXCL13+ CD8+ T cells was identified and found to be enriched in CRC patients.
• In vitro studies demonstrated that tumor cells induce this specific TIGIT+PD-1+CXCL13+ CD8+ T cell phenotype, indicating tumor-driven T cell dysfunction.

Conclusions:

• High TIGIT expression serves as a potential negative prognostic biomarker in colorectal cancer.
• The TIGIT+PD-1+CXCL13+ CD8+ T cell subset represents a novel, tumor-induced T cell phenotype associated with CRC.
• This specific CD8+ T cell population holds promise as a predictive biomarker for immunotherapy response in CRC patients.