CD274 and melanoma: Two biomarkers have been clinically approved for PD-1/PD-L1 blockade therapy: the first is immunohistochemistry (IHC) staining of PD-L1 in non-small-cell lung cancer (NSCLC), melanoma, renal cell carcinoma (RCC), urothelial cancer, and triple-negative breast cancer (TNBC) (6); and the second is high microsatellite instability/defective mismatch repair (MSI-H/dMMR) regardless of tumor type (7, 8).