As shown in Fig. 1C and Supplementary Fig. 3A–D, CTSS expression was positively correlated with PD-L1 (CD274; Spearman’s R = 0.2759, P = 5.097 × 10–9), Tim3 (HAVCR2; Spearman’s R = 0.3111, P = 3.430 × 10–11), PD1 (PDCD1, Spearman’s R = 0.2338, P = 8.460 × 10–7), TIGIT (Spearman’s R = 0.3445, P = 1.537 × 10–13), and LAG3 (Spearman’s R = 0.3485, P = 7.808 × 10–14) in TCGA CRC datasets. Here, PDCD1 is linked to colorectal carcinoma.