BACKGROUND: The use of adoptive T cell therapy has proven to be effective in some advanced malignancies. This study aimed to investigate the effects of lymphocyte-activation gene 3 (LAG-3) immune checkpoint receptor in the enrichment of tumor antigen-specific CD8⁺ T lymphocytes derived from peripheral blood mononuclear cells (PBMCs) in patients with colorectal cancer.

MATERIAL AND METHODS: Peripheral blood samples were obtained from 20 patients with colorectal cancer and apheresis was performed with enrichment and cell sorting to obtain CD8⁺LAG-3⁺ T cells, which were expanded using high-dose interleukin-2 (IL-2). T cell subsets were detected using fluorescence-activated cell sorting (FACS), and T cell receptor (TCR) sequencing was used to determine specific clone types. Interferon-γ (IFN-γ) enzyme-linked immunospot (ELISpot) and cell counting kit-8 (CCK-8) assays were used to measure cell avidity and cytotoxicity.

RESULTS: The cultured cells increased in number over time and had the greatest proliferative activity at 15 days, at which time the percentage of CD3⁺, CD3⁺CD8⁺, and CD8⁺CD28⁺ reached maximal levels. High purity CD8⁺LAG-3⁺ T cells were isolated by FACS and at 15 days. TCR sequencing showed that CD8⁺LAG-3⁺ T cells were oligoclonal, ELISpot identified increased production of tumor-specific IFN-γ, and the CCK-8 assay showed increased cytotoxicity when compared with pre-cultured CD8⁺LAG-3⁻ T cells.

CONCLUSIONS: In patients with colorectal cancer, CD8⁺LAG-3⁺ T cells showed more specific anti-tumor activity following cell culture in vitro, which supported the potential role for the LAG-3 immune checkpoint receptor in enriching tumor-specific T cells in patients with cancer.

Keywords: Blood Cells, Costimulatory and Inhibitory T-Cell Receptors, Cytokine-Induced Killer Cells