The role and function of exosomes in metastasis

Exosomes are small membrane vesicles that play essential roles inintercellular communications. Exosomes contain proteins, lipids,cholesterol, and microRNAs to exchange genetic information betweencells. Metastasis is the migration of cancer cells to other tissues in the bodyand leads the cancer progression. Cancer cells produce more exosomes thannormal cells, and exosomes derived from cancer cells have the potentialability to affect both local and distant microenvironments. Studies haveshown that exosomal integrins (ITGs) play a significant role in specificorgan metastases. Tumor-derived exosomal ITGs can identify metastaticsites of tumor cells. For example, exosomal ITG α۶β۴ and α۶β۱ areassociated with lung metastasis, while ITG β۵ is associated with hepaticmetastasis and ITG β۳ with brain metastasis. Exosomes derived frompancreatic duct adenocarcinoma cells are involved in the determination ofliver metastasis. These exosomes transmit the migration inhibitory factor(MIF) to Kupffer cells and Kupffer cells secrete more transforming growthfactor-beta. Accordingly, fibronectin production increase in hepatic stellatecells. It should be noted that fibronectin accumulation has also a positiveeffect on the formation of pre-metastatic niches. Recent studies reveal thattumor cells are inhibited by reducing the production or altering exosomes,so it can be expected that exosomes play an important role in the treatmentof cancer metastasis.