The discovery of exosomes, which are small, 30-100 nm sized extracellular vesicles that are released by virtual all cells, has initiated a rapidly expanding and vibrant research field. Current investigations are mainly directed toward the role of exosomes in intercellular communication and their potential value as biomarkers for a broad set of diseases. By horizontal transfer of molecular information such as micro RNAs, messenger RNAs, or proteins, as well as by receptor-cell interactions, exosomes are capable to mediate the reprogramming of surrounding cells.
Here, the authors review how especially cancer cells take advantage of this mechanism to influence their microenvironment in favour of immune escape, therapy resistance, tumour growth, and metastasis. Moreover, they provide a comprehensive microarray analysis (n>1,970) to study the expression patterns of genes known to be intimately involved in exosome biogenesis across 26 different cancer entities and a normal tissue atlas. Consistent with the elevated production of exosomes observed in cancer patient plasma, the authors found a significant overexpression especially of RAB27A, CHMP4C, and SYTL4 in the corresponding cancer entities as compared to matched normal tissues. Finally, they discuss the immune-modulatory and anti-tumorigenic functions of exosomes as well as innovative approaches to specifically target the exosomal circuits in experimental cancer therapy.