PDCD1 and lung adenocarcinoma: At the same time, we analyzed the relationship between CRABP2 expression and immune checkpoints in pan-cancer, we found that CRABP2 expression exhibits a significant association with all eight immune checkpoint genes (CD274, PDCD1, CTLA4, PDCD1LG2, HAVCR2, SIGLEC15, LAG3, and TIGIT) in testicular germ cell tumor (TGCT), prostate adenocarcinoma (PRAD), and lung adenocarcinoma (LUAD) (Figure 7H).