Differential expression of TIGIT and ICOS immune check points on lymphocytes in tissues of resected colorectal cancer compared with their counterparts in the peripheral blood and their relations to clinicopathologic characteristics

Abstract Purpose: The current study was carried out to evaluate the expressions of ICOS and TIGIT, on T cells in tissues and peripheral blood of non-metastatic CRC patients, correlating them to different clinicopathologic characteristics of CRC. Methods: We recruited 31 cases of de novo colorectal carcinoma and 25 healthy controls over one year. Interleukin 21 (IL-21) levels were measured in the peripheral blood of both patients and healthy controls using ELISA. Flow cytometry investigated different subsets of T-cell and their expressions of TIGIT and ICOS in both peripheral blood and malignant tissue samples from patients, as well as from normal colonic tissues of CRC patients. Results: The percentages of CD4 + TIGIT + T cells, CD8 + TIGIT + T cells, CD4 + CD8+ TIGIT + T cells, CD4 + ICOS + T cells, and CD8 + ICOS + T cells were significantly higher in malignant CRC tissues compared to normal tissues. Moreover, TIGIT expression on CD4 + and CD8 + T cells was significantly elevated in the peripheral blood of CRC patients compared to controls. Conversely, ICOS expression on CD4 + and CD8 + T cells in peripheral blood was significantly higher in controls than in patients. Additionally, both ICOS and TIGIT expressions were markedly greater on CD8 + T cells, CD4 + T cells, and CD4 + CD8+ T cells in CRC tissues compared to their counterparts in peripheral blood. Conclusion: There was upregulation of immunostimulatory molecules like ICOS, which has been associated with a favourable prognosis. However, the upregulation of immunoinhibitory molecules such as TIGIT predominates, which is linked to disease progression and metastasis.