TIGIT expression in extrahepatic cholangiocarcinoma and its impact on CD8 + T cell exhaustion: implications for immunotherapy.

Extrahepatic cholangiocarcinoma (ECCA) is a malignant tumor. The precise role of T-cell immunoreceptor with Ig and ITIM domains (TIGIT), an emerging immunosuppressive receptor, in ECCA, and its impact on CD8+ T cell exhaustion (Tex) remains unclear. We performed single-cell RNA sequencing (scRNA-seq) to characterize tumor-infiltrating lymphocytes (TILs) isolated from ECCA. We found that TIGIT was significantly overexpressed in TOX+CD8 T cells. Tissue microarray and immunohistochemistry staining demonstrated that increased TIGIT expression was associated with poorer patient survival. Flow cytometry analysis revealed that TIGIT+CD8+ T cells exhibited decreased TNF-α, IFN-γ, and TCF-1 expression, accompanied by elevated PD-1 and TIM-3 expression compared to TIGIT-CD8+ T cells. In the patient-derived xenograft (PDX) model, the anti-TIGIT treatment group demonstrated reduced tumor weight, enhanced CD8 frequency, and an increased IFN-γ proportion compared to the PBS treatment group. The TIGIT antibody-treated group exhibited a notably higher fraction of GRZB, and anti-TIGIT treatment led to elevated TCF-1 protein levels and decreased protein levels of TOX1 and NR4A1. Moreover, TIGIT+CD8 T cells from TILs appear to be in a state of exhaustion with low potential killing capacity in ECCA, as shown by scRNA-seq. Taken together, the present study underscores the significant role of TIGIT in ECCA, contributing to T cell exhaustion and a compromised CD8+ T cell immune response. Targeting TIGIT presents a promising therapeutic avenue to enhance the CD8+ T-cell response, thereby potentially improving ECCA therapeutic benefits.