PD-L1 (B7-H1), a crucial immune checkpoint, is not only expressed on cancer cells and hematopoietic cells including T cells, macrophages, dendritic cells (DCs), et al, but also in some non-hematopoietic tissues including pancreas, vascular endothelium, muscle, skin tissues, et al. PD-L1/PD-1 signaling pathway, as a negative regulatory mechanism against the immune response, plays an important role in tumor evasion from immune surveillance and the occurrence of autoimmune diseases 17. This evidence concerns the gene CD274 and cancer.