PDCD1 and neoplasm: Cordonnier et al. (2020) further confirmed that circulating exosome PD-L1 in melanoma patients plays a role through T lymphocytes in secondary lymphoid organs and through the immunosuppressive PD-1/PD-L1 pathway. Moreover, a large increase in exosome PD-L1 is related to tumor progression (Cordonnier et al., 2020). Chen et al. (2018) demonstrated the presence of melanoma-associated exosome PD-L1 and its immunosuppressive effects and suggested that the exosome PD-L1 level is an indicator to distinguish clinical responders from non-responders.