Furthermore, CRABP2 in LUAD appears to regulate the immune response within the tumor microenvironment by suppressing the expression of certain immune checkpoint molecules, namely CD274 (PD-L1), HAVCR2, and PDCD1LG2 (PD-L2), while promoting the expression of other immune checkpoint molecules, including CTLA4, LAG3, PDCD1 (PD-1), TIGIT, and IGSF8. This evidence concerns the gene PDCD1 and neoplasm.