Furthermore, RBP4 was positively correlated with immune checkpoints, such as VSIR, TIGIT, SIRPA, SIGLEC7, PDCD1, LILRB4, LILRB2, LAG3, HAVCR2, CTLA4, and BTLA, across many cancers, but it showed negative correlations with immune checkpoints in LIHC and TGCT (Figure 5D). This evidence concerns the gene CTLA4 and cancer.