CD274 and metastatic malignant neoplasm: The emergence of immune checkpoint blockade (ICB) therapy that targets programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) or anti-cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) has markedly revolutionized the therapeutic landscape of patients with metastatic cancers [1, 2].