Cancer is one of the leading causes of death worldwide, and this is often attributed to the nonspecific symptoms. Additionally, delayed diagnosis and a lack of treatment options negatively impact prognosis. Recently, the role of extracellular vesicles in cancer progression, specifically, in metastasis and in the capacity of several tumours to invade and colonise specific organs has been established. Reduced oxygen tension due to imbalanced oxygen supply and consumption is termed hypoxia and is one of the most commonly observed features in solid tumours. This is often correlated with poor cancer prognosis. Several reports have established that low oxygen tension (i.e. hypoxia) is a common feature of the tumour microenvironment often enhancing the process of epithelial‐to‐mesenchymal transition (EMT) in cancer cells, thus promoting tumourigenesis and metastasis. Furthermore, hypoxia increases the number of extracellular vesicles released from cancer cells and also modifies their bioactivity and function. The aim of this chapter is to review the association between the tumour microenvironment and extracellular vesicles (EVs), focusing on a specific subpopulation of EVs of endocytic origin, termed exosomes.
Part of the book: Hypoxia and Human Diseases