Moreover, tumor-infiltrating immune cells (TIICs), such as CD8+ T cells, regulatory T cells (Tregs), and tumor-associated macrophages (TAMs), positively affect the clinical outcome of patients with various malignancies, including melanoma, lung cancer, breast cancer, and GC (Adams et al., 2013; Massi et al., 2015; Bremnes et al., 2016; Jiang et al., 2017). This evidence concerns the gene CD8A and gastric cancer.