Cancer Genetics and Epigenetics, 2025, Vol.13, No.3, 106-116 http://medscipublisher.com/index.php/cge 107 2 Biological Characteristics of Exosomes 2.1 The origin, biogenesis and structural composition of exosomes Exosomes belong to nanoscale extracellular vesicles, with diameters typically ranging from 30 to 200 nanometers, and originate from endosomal chambers within cells. Its formation process is that the endosomal membrane indented inward to form polycystic vesicles (MVBs), which contain various cellular substances. When MVBs fuse with the cell membrane, exosomes will be released outside the cell (Edalat et al., 2020; LeBleu and Kalluri, 2020; Feng and Krylova, 2023). This process is strictly regulated and includes steps such as substance sorting, MVBs maturation, and membrane fusion, ultimately generating exosome populations with different molecular compositions (Kim et al., 2021; Yang et al., 2022). Structurally, exosomes are wrapped by a lipid bilayer membrane and contain a large amount of proteins, lipids, nucleic acids (DNA, mRNA, miRNA, lncRNA), and metabolites. These components can reflect the cellular origin of exosomes and whether the cells that produce them are in a normal or diseased state. The key components in exosomes include quad-transmembrane proteins (CD9, CD63, CD81), heat shock proteins and various signaling molecules, which make the structure of exosomes stable and their functions diverse (Qasim et al., 2019; LeBleu and Kalluri, 2020; Ayala-Mar et al., 2021; Dong et al., 2023). The special molecular characteristics of exosomes make them promising as markers for disease diagnosis and carriers for treatment. 2.2 Stability and transmembrane transport characteristics of exosomes Exosomes are very stable in biological body fluids, which is attributed to their lipid bilayer structure. It can protect the substances carried by exosomes from being decomposed by enzymes and is not afraid of harsh extracellular environments. This stability enables exosomes to circulate for a long time in body fluids such as blood, making them highly suitable for liquid biopsy and drug transport (Qasim et al., 2019; LeBleu and Kalluri, 2020). Moreover, exosomes have good compatibility with the human body and are less likely to trigger immune responses, thus having more advantages in clinical applications (Dong et al., 2023; Chen, 2024). Exosomes can cross biological barriers and transport the substances they carry to nearby or distant cells. It can be selectively absorbed by target cells through methods such as endocytosis, membrane fusion, or binding to receptors, thereby transferring bioactive molecules there (Edalat et al., 2020; Gurung et al., 2021; Ayala-Mar et al., 2021; Feng and Krylova, 2023). This precise transportation ability plays a key role in the transmission of information and regulation of cell functions by exosomes between cells. 2.3 The role of exosomes in intercellular communication and signal transduction Exosomes are important media for information transmission between cells. They can transport proteins, lipids and nucleic acids, and regulate various processes of the body's normal operation and illness. By transmitting these molecules, exosomes can alter the gene expression and signal transduction pathways of other cells, influencing immune responses, tumor development, tissue repair, etc. (Kourembanas, 2015; Qasim et al., 2019; Edalat et al., 2020; LeBleu and Kalluri, 2020; Kim et al., 2021; Dong et al., 2023). This ability to change the state of cells is the root cause of the significance of exosomes in the research of diseases such as cancer. During the process of cellular signal transduction, different substances carried by exosomes can activate or inhibit specific signal transduction processes in the target cells. For instance, exosomes produced by tumors may carry oncogenes, oncoproteins, or signal proteins that help tumors grow, metastasize, and evade the immune system (LeBleu and Kalluri, 2020; Yang et al., 2022; Dong et al., 2023). On the other hand, exosomes can also deliver therapeutic molecules or substances that regulate the immune system, which indicates that they can play a dual role in the development and treatment of diseases. The process by which exosomes transmit signals is complex and can be affected by the environment. It is precisely for this reason that they have great potential in disease diagnosis and treatment. 3 The Functional Roles of Tumor-Derived Exosomes 3.1 Promote the proliferation, invasion and metastasis of tumor cells Tumor-derived exosomes (TEXs) play a crucial role in the process of tumor deterioration, promoting the
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