CEACAM1 and gastric adenocarcinoma: A positively correlation was also noted between mRNA expression of CEACAM-1 or MHC class II and that of PD-L1 in TCGA stomach adenocarcinoma tissue dataset (r = 0.22 and p < 0.0001, r = 0.42 and p < 0.0001 respectively) (Fig. 1c).