CD274 and cancer: For instance, Zhang has reported a potential biomarker exosomal Programmed cell death 1 ligand 1 (PD−L1) for immunotherapy and provided SERS detection platform for the trace detection of clinical cancers, the detection limit for PD−L1 and exosomes based on PD−L1 were 0.1 ng mL−1 and 4.8 × 106 particles mL−1, respectively [13].