CD274 and lung carcinoma: Kim et al. found that in lung cancer cell lines the amount of exosomal PD-L1 in the culture supernatant represented the amount of PD-L1 expression on the cell surface, while the abundance of exosomal PD-L1 isolated from plasma of non-small-cell lung cancer (NSCLC) patients correlated with tumor PD-L1 positivity [28].