As ligands of PD-1, B7-H1 (PD-L1) could be expressed in many types of cells, including tumor cells, immune cells, epithelial cells, and endothelial cells, whereas B7-DC (PD-L2) is primarily expressed in antigen-presenting cells (APCs), such as macrophages and DCs [6]. This evidence concerns the gene CD274 and neoplasm.