PDCD1 and breast cancer: Based on tumor and normal samples from The Cancer Genome Atlas (TCGA) and the Genotype-Tissue Expression (GTEx) databases via GEPIA2 [16], we firstly analyzed the mRNA expression of the main members of TIGIT-PVR/CD155 (Fig. S3A) and PD-1/PD-L1 (Fig. S3B) signaling in breast cancer (BRCA), colon adenocarcinoma (COAD), rectal carcinoma (READ), and liver hepatocellular carcinoma (LIHC).