Exosomes are extracellular vesicles (EVs) that play an important role in cellular communication. Exosomes are secreted almost by all types of cells including normal (healthy) cells, cancer cells, and stem cells such as cancer stem cells (CSCs) or mesenchymal stem cells (MSCs). Cellular communication can be induced by the exosomal contents, consisting of proteins, DNA and RNA cargo (especially microRNA and long non-coding RNA), and metabolomes. The role and composition of exosomal contents varies depending on the source of the exosome. For example, exosomal RNA cargo derived from CSCs plays an important role in tumor progression, while that derived from MSCs mostly helps in remedying disease.

To study the role of CSC- and MSC-derived exosomes in cancer progression and treatment, respectively, it is crucial to know the exact exosomal contents associated with cancer progression and treatment. Unlike RNA cargoes, metabolomes, which are a set of biomolecules closely related to the cell phenotype, have so far been given less attention. Exosomal metabolomes can be detected in blood and other body fluids and can be used as potential diagnostic markers in diseases, including cancer. These metabolomes are also released from cells cultured in the lab (in vitro) and their composition differs according to the type of cells and culture condition. Despite an encouraging start in depicting the role of in vitro cell-derived exosomal metabolomes in cellular communication, less data is available regarding the in vivo role of exosomal metabolomes in body fluids. Precise identification of exosomal RNA cargo and metabolomes, in particular those derived from CSCs and MSCs, may soon deliver useful information on the phenotype of cancer cells and give novel biomarkers for disease detection, prognosis, and treatment.

This Special Issue welcomes both original research and review articles that advance our understanding of the role of CSC- and MSC-derived exosomal RNA cargo and metabolomes in cancer pathogenesis, diagnosis, and treatment. We are interested in articles related to the detection of novel RNA cargoes (microRNA and lncRNA) and metabolomes of CSC- and MSC-derived exosomes and their function in cancer pathogenesis, how they can be used as useful diagnostic or prognostic markers, and therapeutic tools.

Potential topics include but are not limited to the following:

• Cross talk between cancer stem cells, their exosomes, and the tumor microenvironment
• Cross talk between MSCs, their exosomes, and the microenvironment
• The role of CSC-derived exosomal RNA cargo (microRNA and lncRNA) in cancer progression
• The role of CSC-derived exosomal metabolomes in cancer progression
• The role of CSC-derived exosomal RNA cargo in cancer diagnosis and prognosis
• The role of CSC-derived exosomal metabolomes in cancer diagnosis and prognosis
• The role of MSC-derived exosomal metabolomes in disease treatment