In brief, IGFBP-1 [47], IGFBP-2 [48], IGFBP-3 [49], and IGFBP-5 [50] have been shown to elevate PD-L1 expression on macrophages and tumor cells, leading to reduced immune response in gliomas, esophageal, and colorectal cancers. This evidence concerns the gene IGFBP2 and central nervous system cancer.