PDCD1 and digestive system cancer: The results showed that high-risk score group was positively correlated with high expression of HAVCR2 in four digestive system cancers (Figure 8); with high expression of CD274 in CRC, ESCA and STAD; with high expression of PDCD1 in CRC, ESCA and LIHC; with high expression of LAG3 in CRC and STAD; with high expression of CTLA4 and TIGIT in CRC and LIHC (P < 0.05) (Figure S3).