CD274 and cancer: PD-L1 of tumor stromal components, such as fibroblast, extracellular matrix (ECM), tumor associated macrophages (TAM), and myeloid derived suppressor cells (MDSC) deactivates T-cell (CD8+) mediated cancer cells killing through interaction with PD-1 In review on T-cell surface (Sznol and Chen, 2013; Turley et al., 2015).