Studies have shown that the CD4 + /CD8 + ratio is significantly decreased in patients with some cancers (such as breast cancer, gastric cancer, and lung cancer) (Wang et al., 2013; Dias Rodrigues et al., 2017; Liu, 2022), HIV (Castilho et al., 2019), and neuromyelitis optica spectrum disorders (Yang et al., 2021), indicating that the immune function of patients may be reduced. This evidence concerns the gene CD8A and breast cancer.