Somayeh Keshtkar - Department of Molecular Medicine, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences
Negar Azarpira - Transplant Research Center, Shiraz University of Medical Sciences
Mohammad Hossein Ghahremani - Department of Molecular Medicine, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences

Exosomes, membrane vesicles of 40_100 nm in diameter, are derived from endosomes in various cells and contain a cargo that include miRNA, mRNA, and proteins. The bioactive molecules specifically packed into exosomes can be transferred into recipient cells changing their biological properties, by which tumour cells continuously modify their surrounding microenvironment and distant target cells favouring cancer metastasis. It has been suspected for a long time that exosomes participate in the whole process of tumour metastasis. Since these exosomes are easily accessible and capable of representing their parental cells, exosomes draw much attention as a promising biomarker for tumour screening, diagnosis and prognosis. In the mean time, cancer researchers are finding biomarkers for utilize in personalized medicine. In personalized medicine, the customized treatment depends on information about the molecular characteristics of the cancer signature, especially the personalized diagnostics. Although traditional biomarkers have been widely and maturely utilized in personalized medicine, their inherent limitations cannot be ignored. First, the most common method to detect pharmacogenomically relevant sequences is fluorescence in situ hybridization, which depends on the sample from biopsy. Secondly, tissue biopsy, the best method of diagnosis, is invasive and dangerous, and is unable to be applied to repeated diagnosis. Thirdly, the low specificity of serum biomarkers in present clinical diagnosis may contribute to a low efficiency of diagnosis. While exosomes ,compared with traditional biomarkers, possess great potential as cancer biomarkers in personalized medicine. Firstly, exosomes can travel across the endothelium into the circulation allowing serum detection. Secondly, exosomes are akin to vessels enriched with much information about the parental cells, and the cargoes in exosomes are protected by the phospholipid bilayer from degradation by proteinases and nucleases. Consequently, biomarkers at a relatively low expression are much easier to be detected through isolating exosomes. Thirdly, analysing the fraction of exosomes can effectively weaken the serum matrix effect and reduce the dynamic range. Fourthly, exosomes are constituently secreted by various cells and the number of exosomes increases obviously in the serum of cancer patients. Accordingly, it is reasonable to assume that the representativeness of exosomes is better than fine needle biopsy, which is of great meaning for the accuracy of personalized diagnostics. Even though the isolation of exosomes is a troubling issue, exosomes have the potential to be used in clinical practice in the near future as the field rapidly expands.

exosome ; personalized diagnostics; cancer biomarkers