LAUSR

Cancer is a well-known, yet poorly understood disease. In which, a healthy tissue is morphed into a cancerous tissue through an intricate, multistep process. This polymorphism has been the focus of cancer research for many decades. Scientists have agreed on a set of traits that are thought to be shared by all cancer tissue types, these traits include; enabling proliferation, evading growth suppressors, resisting cell death, replicative immortality, inducing angiogenesis, and initiating invasion and metastasis, along with other enabling characteristics (Hanahan and Weinberg, 2000; Hanahan and Weinberg, 2011). As researchers investigate the development and propagation of these traits, or as they are called the “hallmarks” of cancer, it became evident that cancer cell-derived extracellular vesicles (EVs), particularly exosomes, play a major role in almost all of them. In the late 1940s, it was recognized that cells release spherical shaped particles called EVs (Chargaff and West, 1946). Then, almost 40 years later, “exosomes” were acknowledge as a distinct sub-type of EVs (Trams et al., 1981). Up tell now, it is technically challenging to obtain a pure fraction of a specific EV sub-type, due to similarities shared amongst these vesicles. However, the International Society for Extracellular Vesicles, have released a position statement on the minimal experimental requirements for definition of EVs and their functions (MISEV2014; updated in 2018; MISEV2018) (Lotvall et al., 2014; Théry et al., 2018). The MISEV distinction between the different EV sub-types realize on size, density, morphology, subcellular origin, and composition. This was done in order to make scientific reporting on EV biology more consistent and reliable. Most published literature on EVs, including the literature on the role of EVs in cancer, use the term “exosomes” to refer to the EV sub-type under study. These studies include a section that describes the method of “exosome” isolation, and at least a couple of characterization techniques, to justify their nomenclature. Characterization of exosomes in published literature is often based on size and “exosome-enriched” proteins content verification. On the other hand, the concept of “cancer stem cell” (CSC) only emerged in the 1990s (Lapidot et al., 1994), with a lot of controversy and a number of proposed theories following it. Some say that CSC arise as a result of normal stem cell mutation, while others suggests that CSC arise as a result of a somatic cell acquiring erroneous stem cell characteristics, turning it into cancerous stem cell that can differentiate into heterogeneous population of cancer cells (Baccelli and Trumpp, 2012).