CD274 and cancer: Numerous reports have indicated that PD-L1 expression is regulated by different intrinsic and extrinsic mechanisms, including genomic alterations, post-transcriptional regulations, post-translational modifications of proteins, carcinogenic signals, inflammatory cytokines, etc. Increased PD-L1 expression in TME restricts host immune responses and induces the development of an immunosuppressive microenvironment in cancer [171, 172].