CD274 and neoplasm: The underlying mechanisms of melanoma immune evasion are reasonably well understood and include downregulation of tumor-associated antigens (e.g., MART-1, tyrosinase, and gp100, cancer testis antigens, neoantigens), upregulation of co-inhibitory receptor ligands such as PDL-1 [17,37], downregulation of MHC-I-class molecules [17,38,39,40] and a plethora of further mechanisms contributing to a tumor-promoting microenvironment [17].