It is clear that exosomes (endosome derived vesicles) serve important roles in cellular communication both locally and distally and that the exosomal process is abnormal in
cancer.
Cancer cells are not malicious cells; they are cells that represent 'survival of the fittest' at its finest. All of the mutations, abnormalities, and phenomenal adaptations to a hostile microenvironment, such as
hypoxia and nutrient depletion, represent the astute ability of
cancer cells to adapt to their environment and to intracellular changes to achieve a single goal - survival. The aberrant exosomal process in
cancer represents yet another adaptation that promotes survival of
cancer.
Cancer cells can secrete more exosomes than healthy cells, but more importantly, the content of
cancer cells is distinct. An illustrative distinction is that exosomes derived from
cancer cells contain more
microRNA than healthy cells and unlike exosomes released from healthy cells, this
microRNA can be associated with the
RNA-induced silencing complex (RISC) which is required for processing mature and biologically active
microRNA.
Cancer derived exosomes have the ability to transfer metastatic potential to a recipient cell and
cancer exosomes function in the physical process of invasion. In this review we conceptualize the aberrant exosomal process (formation, content selection, loading, trafficking, and release) in
cancer as being partially attributed to
cancer specific differences in the endocytotic process of receptor recycling/degradation and plasma membrane remodeling and the function of the endosome as a signaling entity. We discuss this concept and, to advance comprehension of exosomal function in
cancer as mediators of communication, we detail and discuss exosome biology, formation, and communication in health and
cancer; exosomal content in
cancer; exosomal
biomarkers in
cancer; exosome mediated communication in
cancer metastasis, drug resistance, and interfacing with the immune system; and discuss the therapeutic manipulation of exosomal content for
cancer treatment including current clinical trials of exosomal
therapeutics. Often referred to as cellular nanoparticles, understanding exosomes, and how
cancer cells use these cellular nanoparticles in communication is at the cutting edge frontier of advancing
cancer biology.