Concentration of co-inhibiting immune checkpoints and their ligands in blood of patients with colon tumor

Abstract

Tumor cells can modulate the immune response using co-inhibiting immune checkpoints, which allows them to “escape” from immunity. The aim of this study was to measure concentrations of co-inhibiting immune checkpoints (CTLA-4, TIM-3, LAG-3, PD-1) and their ligands (B7-2, Galectin-9, PD-L1) in blood serum of patients with colon tumor. Methods. The study included 44 patients with colorectal cancer, 25 patients with benign colon tumors, and 25 patients of the control group (patients after plastic surgery for colostomy that had been formed earlier due to colon injury). Blood concentrations of co-inhibiting immune checkpoints (CTLA-4, PD-1, TIM-3, LAG-3) and their ligands (B7-2, Galectin-9, PD-L1) were measured by flow cytofluorometry with a CytoFlex LX analyzer (Beckman Coulter, USA) using a LEGENDplex ™ HU multiplex analysis kit (Immune Checkpoint, USA). Results. In patients with colon cancer, the serum concentrations of co-inhibiting immune checkpoints (TIM-3, CTLA-4, LAG-3) were higher than in the control group. The level of TIM-3 protein increased by 11.7 times (p<0.001), CTLA-4 by 2.77 times (p<0.001), and LAG-3 by 2.42 times (p=0.02). Also, in patients with colorectal cancer, the concentration of TIM-3 exceeded the value in patients with benign colon tumor by 7.1 times (p<0.001) and LAG-3 by 2.4 (p=0.01) times. In patients with malignant colon neoplasm, the level of TIM-3 ligand (Galectin-9) was higher than in the control group by 33.3 times (p<0.001) and the level of CTLA-4 ligand (B7-2) by 2.51 times (p=0.002). Conclusion. The increases in CTLA-4, TIM-3, LAG-3, and their ligands B7-2 and Galectin-9 indicate the participation of these co-inhibiting molecules in the pathogenesis of colorectal cancer. When analyzing the data, we identified parameters that may be essential in a diagnostic model for determining the probability of oncological pathology.