CD274 and cancer: Various studies have confirmed that PD-L1 and PD-L2 are expressed in cancer cells, T cells, macrophages (mostly M2 macrophages), myeloid DCs (dendritic cells), myeloid suppressor cells, stromal fibroblasts, and endothelial cells, suggesting that PD-1/PD-L1/PD-L2 can influence many cell types.