CD63 and neoplasm: The presence of common exosome markers, tetraspanins CD81 and CD63 which are present on a fraction of exosomes and can be used to differentiate exosomes from other EVs (34), as well as PD-L1 were evaluated in PKH26+ (red, tumor) or PKH67+ (green, fibroblast) EVs from each model isolated following 3, 6, and 12 days culture (Figures 4E, F; representative image strips, Figure 4G).