CD8A and colorectal cancer: Studies have found that CD8+ Trm in colorectal cancer patients has specific demethylation of CD103 and CD39-related genes (65), CD103+CD39+ T cells have a strong MHC-dependent tumor killing ability, and the co-expression of CD103 and CD39 is also considered to be the key to T cell tumor-specific recognition characteristics and differentiation from bystander T cells, and can be used as an independent risk factor for the prognosis of colorectal cancer (65, 119).