Exosomes have been shown to have a role in tumorigenesis through the regulation of angiogenesis, the immune response, and metastasis.
What are the Functions of Exosomes?
There is still not a clear definitive answer as to exosomes functions within the cell. Previous theories have suggested that exosomes are created to remove excessive or non-functional cellular components and to recycle surface proteins, however this has not been entirely proven as fact. The environment within and outside the cell affect the number and quality of the exosomes generated. Synthesis of exosomes is thought to be associated with some specific proteins. The internal components of exosomes can be transferred from cell to cell; important mediator of intercellular communication.
When a person has cancer, the body produces twice the amount of exosomes seen in a healthy individual. It is unknown as to why this occurs.
How are Exosomes Generated?
First budding of the plasma membrane creates intracellular endosomes. The intracellular endosomes generate multivesicular bodies (MVBs) that fuse with lysosomes. After fusion, the cells are either degraded or fuse with the plasma membrane which then causes the release of exosomes into the extracellular space.
Immune cells, mesenchymal stem cells, fibroblasts, neurons, endothelial cells, and epithelial cells all produce exosomes.
What do Exosomes Contain?
The internal components of an exosome greatly determine its effects. Exosomes contain a multitude of different types of proteins, lipids, and nucleic acids.
Function of Exosomes in Cancer
Exosomes seem to encourage tumor growth. There is also evidence to suggest that exosomes have anticancer functions that inhibit tumor growth and disease progression. They can be used in the diagnosis of certain cancers.
Unique nucleic acids can be identified in cancer exosomes and can be used as disease markers in disease diagnosis.
Proteins in exosomes reflect their lineage making them useful in the diagnosis of certain conditions.
Exosomes can activate fibroblasts which allows for the formation of blood vessels that provides tumors with oxygen and nutrients.
Exosomes are able to regulate tumor growth and metastasis.
Function of Exosomes in Cancer Therapies
Exosomes are currently thought to increase the rate of progression in certain cancers; however more research is needed to determine the entirety of their role. Exosome presence can reduce chemotherapy effectiveness as they have been seen to remove “chemotherapeutic agents from target cancer cells.”
Exosomes are therapeutically being used as delivery vesicles to move genetic material to specific targets. The genetic modification of exosomes may someday lead to the control of tumors and metastasis.