CD47 and cancer: Similar analysis done on exosomes derived from other cancer and non-cancer cell lines suggested that CD47 is not a common marker of exosomes, and that this should be taken into account when interpreting the circulation profile of exosomes (Fig. S10). This highlights the importance of the endowment of active targeting moieties such as expression of targeting ligands as fusion constructs on exosomal surface proteins 15, 31, as well as developing strategies to bypass the RES organs as described above for effective targeted in vivo delivery of exosomes to non-RES sites such as tumours.