In patients with metastatic MeL, the levels of circulating exosomal PD-L1 are positively associated with IFN-γ levels and exhibit changes during anti-PD-1 therapy, suggesting that exosomal PD-L1 may serve as a predictive marker for the outcomes of anti-PD-L1 treatment 29. This evidence concerns the gene CD274 and melorheostosis.