CD274 and cancer: PD-L1 is commonly expressed on T-cells, B-cells, macrophages, cancer cells, and DCs and is upregulated through the release of pro-tumor cytokines (such as interleukin-4 (IL-4), IL-10, and vascular endothelial growth factor (VEGF)) from cancer cells and is associated with poor prognosis (11, 12).