Small endogenous vesicles called exosomes are beginning to be explored as drug delivery vehicles. The in vivo targets of exosomes are poorly understood; however, they are believed to be important in cell-to-cell communication and may play a prominent role in cancer metastasis.
Researchers at the University of Colorado Denver aimed to elucidate whether cancer derived exosomes can be used as drug delivery vehicles that innately target tumors over normal tissue. Their in vitro results suggest that while there is some specificity towards cancer cells over “immortalized” cells, it is unclear if the difference is sufficient to achieve precise in vivo targeting. Additionally, they found that exosomes associate with their cellular targets to a significantly greater extent (>10-fold) than liposomes of a similar size. Studies on the association of liposomes mimicking the unique lipid content of exosomes revealed that the lipid composition contributes significantly to cellular adherence/internalization. Cleavage of exosome surface proteins yielded exosomes exhibiting reduced association with their cellular targets, demonstrating the importance of proteins in binding/internalization.