KLRC1 and colorectal cancer: NKG2A+ NK cells infiltrate the tumor microenvironment, and increased expression of NKG2A in NK cells has been observed in patients with non-small cell lung cancer (28, 29), breast cancer (30), colorectal cancer (31, 32), acute myeloid leukemia (33, 34), hepatocellular carcinoma (35), breast cancer (36), cervical cancer (32), etc. A large proportion of NK cells with high NKG2A expression has also been found in tumor-draining lymph nodes (36).