Abstract: Background and purpose: Colorectal cancer (CRC) is a disease that seriously affects the quality of life. This study aimed to investigate the subsets and significance of tumor cell microenvironment T cell in CRC and adenoma. Methods: Immunohistochemistry and flow cytometry were used to test T lymphocyte subsets in 51 healthy subjects (control group), 46 patients with colorectal adenomas (adenoma group), 100 CRC patients (cancer group), and 15 postoperative patients with CRC (postoperative group). Results: The positive rates of CD4⁺ T cells in the control group, adenoma group and cancer group were 90.00%, 43.75% and 32.65%, respectively. The positive rates of CD8⁺ T lymphocytes were 30.00%, 56.25% and 75.51%, respectively. The positive rates of CD28⁺ T lymphocytes were 42.86%, 30.00% and 20.00%, respectively. The levels of CD4⁺, CD4⁺/CD8⁺, CD28⁺, CD8⁺CD28⁺ and CD8^－CD28⁺ in the control group, adenoma group and cancer group gradually decreased, while the CD8⁺ and CD8⁺CD28^－ levels gradually increased (P<0.05). The difference in T cell subsets between preoperative and postoperative patients was statistically significant (P<0.05). Conclusion: CD4⁺, CD4⁺/CD8⁺, CD28⁺, CD8⁺CD28⁺ and CD8^－CD28⁺ in the subgroup of colorectal tumor microenvironment showed a declining trend, while CD8⁺ and CD8⁺CD28^－ showed an increasing trend. Moreover, these trends gradually appeared in precancerous adenomas. After CRC patients underwent tumor resection, their T cell subsets recovered. Therefore, to some extent, the changes of T cell subsets in CRC can predict the development of colorectal disease early.

Key words: Tumor microenvironment, Colorectal cancer, Colorectal adenoma, T lymphocyte subsets, Flow cytometry