Interestingly, we found that TFAP4 was negatively correlated with the expression levels of PD1 (PDCD1) and CTLA4 in BLCA, COAD, LGG, LUSC, PCPG, SKCM, TGCT, UCEC and UVM, but positively correlated with KIRC and LIHC, suggesting that TFAP4 might regulate the immune response in these cancer types. This evidence concerns the gene PDCD1 and bladder transitional cell carcinoma.