We evaluated the correlation between the number of tumor infiltrating CD8 positive T cells and expression levels of inhibitory immune checkpoint ligands, including ligand for PD-1 (PD-L1), ligand for Tim-3 (CEACAM-1), and ligands for Lag-3 (LSECtin and MHC class II) on tumor cells, and the correlation between inhibitory ligands by interrogating TCGA stomach adenocarcinoma tissue dataset and by performing the multiplex immunohistochemistry (IHC) staining in surgically resected GC samples. This evidence concerns the gene CEACAM1 and gastric adenocarcinoma.