Our findings revealed that PTTG1 is positively correlated with both CTLA-4 and PD-1 in some tumors such as ACC, KICH, and HNSC, which may indicate that PTTG1 could be a novel biomarker for PD-1 in these tumors (Figure 8A). Here, PDCD1 is linked to adrenal cortex carcinoma.