CD274 and melanoma: Importantly, melanoma is an immunologically hot tumor, which is characterized by a TME rich in tumor-infiltrating lymphocytes (TILs such as cytotoxic CD8+ T-cells and NK cells), immune checkpoint (IC) ligands such as programmed death ligand 1 (PD-L1) overexpression on tumor cells, genomic instability, and pre-existing antitumor immune response [28,29].