Interestingly, many studies have demonstrated that the level of NKG2A expression in intratumoral cytotoxic T and NK cells is also higher than that in peripheral blood of patients with liver cancer, head and neck squamous cell carcinoma, esophageal cancer, gastric cancer, ovarian cancer, cervical cancer, or breast cancer (André et al., 2018, van Montfoort et al., 2018, Abd Hamid et al., 2019, Sun and Sun, 2019, Rethacker et al., 2022). This evidence concerns the gene KLRC1 and breast cancer.