Cancer Genetics and Epigenetics, 2025, Vol.13, No.3, 106-116 http://medscipublisher.com/index.php/cge 108 continuous growth of tumor cells, their invasion of surrounding tissues and metastasis. They can change the environment around the tumor, facilitate the formation of new blood vessels, and trigger epithelial-mesenchymal transition (EMT), all of which are important steps in tumor metastasis. TEXs can also promote the formation of the pre-metastatic microenvironment and make tumor cells more likely to invade and take root in distant tissues by delivering carcinogenic proteins and RNA to other cells (Zhang et al., 2018; Yousefi et al., 2019; Sun et al., 2021; Alavizadeh et al., 2022; Gao et al., 2025). These exosomes can alter the states of other cells, such as stromal cells and immune cells, creating an environment conducive to tumor growth. TEXs can adjust the permeability of blood vessels, weaken the immune system's monitoring of tumors, enable tumor cells to survive in the blood, and form new tumors. Some molecules in TEXs, such as specific micrornas and proteins, are directly involved in these processes, making them key factors in cancer metastasis (Zhang et al., 2018; Yousefi et al., 2019; Sun et al., 2021; Wang et al., 2022; Gao et al., 2025). 3.2 Participate in immune evasion and drug resistance mechanisms TEXs play a significant role in helping tumors evade attacks from the immune system. They can regulate the activity of various immune cells around the tumors. It can inhibit the functions of T cells, natural killer cells (NK), and dendritic cells, promote the increase of regulatory T cells and myeloid-derived suppressor cells, thereby forming an environment that enables tumor cells to evade immune examinations (Alavizadeh et al., 2022; Sarmadian et al., 2024; Gao et al., 2025). The hypoxic environment can make the immunosuppressive effect of TEXs stronger and better inhibit the anti-tumor response of immune cells (Yin et al., 2022). In addition to affecting immune function, TEXs is also associated with tumor drug resistance. They transfer molecules related to drug resistance, such as specific micrornas and proteins, to tumor cells that were originally sensitive to drugs, causing these cells to develop drug resistance. TEXs can also isolate therapeutic drugs or change the targets of drug action, reduce the efficacy of anti-cancer treatment, and lead to tumor recurrence and further deterioration (Zhang et al., 2018; Yousefi et al., 2019; Alavizadeh et al., 2022; Gao et al., 2025). 3.3 Specific molecular carriers reflecting the state of the tumor TEXs encapsulate a variety of biomolecules, including micrornas (miRNAs), long non-coding Rnas (lncRNAs), and proteins. These molecules can reflect the characteristics of the tumor cells from which they originate. These molecules transmit information between cells and are involved in regulating the gene expression, signal transduction processes and cellular activities of other cells (Zhang et al., 2018; Alavizadeh et al., 2022; Gao et al., 2025). For instance, micrornas in exosomes can prevent certain genes from being expressed. Long non-coding Rnas can adsorb micrornas or regulate gene transcription, thereby influencing the growth and metastasis of tumors (Wang et al., 2022; Zhang et al., 2022). These molecules in TEXs not only have important functions, but also can serve as biomarkers for cancer diagnosis and prognosis determination. The presence and content of specific micrornas, long non-coding Rnas and proteins in TEXs can reflect the type, development stage and therapeutic effect of tumors, which enables them to be applied in liquid biopsy to achieve non-invasive cancer monitoring and personalized treatment (Alavizadeh et al., 2022; Wang et al., 2022; Zhang et al., 2022; Gao et al., 2025). 4 The Diagnostic Potential of Exosomes in Liquid Biopsy 4.1 Stable exosomes are present in various body fluids suitable for non-invasive sampling Exosomes are abundantly present in various body fluids such as blood, urine, saliva and breast milk, which enables people to conveniently obtain them through non-invasive means for liquid biopsy (Jafarbeik-Iravani et al., 2017; Song et al., 2020; Cai et al., 2022). The lipid bilayer structure of exosomes is very stable, which can protect the molecules inside from being decomposed by enzymes and is not afraid of the harsh extracellular environment. In this way, during the collection and processing, the information used for diagnosis can remain complete (Qin et al., 2018; Breakefield et al., 2021; Wang et al., 2025).
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