Dysfunctional role of elevated TIGIT expression on T cells in oral squamous cell carcinoma patients.

Objective: This study was aimed to analyze the role of T‐cell immunoreceptor with immunoglobulin and tyrosine‐based inhibitory motif domains (TIGIT) expression on T cells in patients with oral squamous cell carcinoma (OSCC). Materials and Methods: Peripheral blood mononuclear cells (PBMC) and tumor‐infiltrating lymphocytes (TILs) were collected from OSCC patients. The correlation between TIGIT expression and clinicopathologic features was analyzed by chi‐square test. Phenotypic and functional study of TIGIT+ T cells were performed by flow cytometry. Results: TIGIT was highly expressed on T cells from PBMC and TILs. High expression of TIGIT on CD4+ T cells (19.0%) and CD8+ T cells (35.9%) was also associated with higher T stage and nodal invasion. Moreover, TIGIT+CD4+ and TIGIT+CD8+ T cells sorted from OSCC patients showed a dysfunctional phenotype (low cell proliferation and low secretion of IL‐2, TNF‐α and IFN‐γ), and TIGIT+CD4+ T cells exhibited inhibitory function (high expression of Foxp3 and high amounts of IL‐10). Importantly, TIGIT blockade can enhance the proliferation ability and effective cytokine production (IL‐2, TNF‐α, and IFN‐γ) of CD4+ and CD8+ T cells from OSCC patients in vitro. Conclusions: TIGIT‐expressing T cells exhibit a lower effector cytokine‐releasing phenotype in OSCC patients. [ABSTRACT FROM AUTHOR]