PDCD1 and liver cancer: The result showed that PD-1, PD-L1, CTLA4, and PD-L2 might positively correlate with AC099850.3 based on 31 liver cancer tissue (Figure 7D, PDCD1: r = 0.341, P = 0.012; CD274: r = 0.239, P = 0.04; CTLA4: r = 0.314, P = 0.006; PDCD1LG2: r = 0.159, P = 0.16).