Tumour metastasis is a highly orchestrated, multistep process encompassing local invasion, intravasation, survival in the circulation, extravasation and colonisation of distant organs. A central mechanism underlying this process involves tumour-derived EVs, which facilitate organotropic metastasis and remodel the pre-metastatic niche by selectively delivering bioactive proteins, thereby promoting tumour cell invasion and dissemination (13).

The specific targeting of EVs to distant organs mainly depends on integrin family proteins, such as α6β4 and αvβ5, on the vesicle membrane surface. Integrins are important molecules that mediate cell-extracellular matrix adhesion and confer organ tropism on vesicles. Different integrin heterodimers can be recognised and taken up by vascular endothelial cells in specific target organs. For example, EVs carrying integrin αvβ3 tend to target lung tissue, whereas integrins α6β4 and αvβ5 are associated with liver and brain metastasis, respectively (14). Clinical studies have also confirmed that breast cancer-derived EVs can target and interact with lung tissue endothelial cells by delivering integrin αvβ3, thereby activating local S100 protein expression, promoting formation of a pre-metastatic microenvironment in the lung and creating favourable conditions for the colonisation of circulating tumour cells (15,16).

Following the preliminary formation of the pre-metastatic niche, EVs deliver hydrolases, including matrix metalloproteinases (MMPs). Encapsulated within vesicles and trafficked to the local microenvironment of target organs, these hydrolases specifically degrade extracellular matrix (ECM) structural proteins, disrupt tissue barriers and trigger matrix remodelling, thereby clearing physical obstacles to tumour cell invasion and the establishment of metastatic foci (17). For example, cervical cancer-derived EVs deliver MMP-14 to recipient cells, markedly enhancing ECM remodelling efficiency by activating the ERK signalling pathway and accelerating remodelling of the tumour metastatic microenvironment (18). Furthermore, EV-mediated ECM remodelling itself forms a positive feedback loop that augments the invasive potential of tumour cells. Neuroblastoma-secreted EVs are enriched with a disintegrin and metalloproteinase 10 (ADAM10); after transport to the local microenvironment via vesicles, ADAM10 directly facilitates local invasion and directed migration of tumour cells (19).

Moreover, integrins and the ECM are functionally interdependent rather than independent entities. As pivotal transmembrane receptors, integrins mediate bidirectional communication between cells and the ECM. Integrins facilitate cell-ECM adhesion and transduce extracellular cues into intracellular signalling cascades, thereby critically regulating tumour invasion and metastasis (19). For example, β1 integrin is consistently endogenously upregulated in multiple human malignancies. β1 integrin promotes tumour cell adhesion to specific ECM components (20), such as fibronectin and collagen, and activates downstream effectors, including FAK, Src and PI3K/Akt pathways. Concurrently, it orchestrates cytoskeletal reorganisation through Rho GTPase-mediated actomyosin contractility, collectively enhancing metastatic capacity (21). Furthermore, integrins serve as mechanosensors that detect ECM stiffness, topography and ligand density. Integrins on the surface of EVs also possess mechanosensory functions. This mechanical input is integrated with biochemical signals, particularly through crosstalk with Rho family GTPases, to coordinate polarised cytoskeletal dynamics and directional tumour cell migration (22).

In terms of clinical translation of the aforementioned mechanisms, applications can be categorised into three major dimensions. First, integrin subtypes present on the EV membrane surface can serve as predictive biomarkers for organ-specific metastasis. Supported by the experimental and literature evidence outlined as aforementioned, the endogenous upregulation of integrin αvβ3 indicates an elevated risk of pulmonary metastasis in breast cancer, whereas the natural high expression of integrins α6β4 and αvβ5 is associated with liver and brain metastasis, respectively. In addition, ADAM10 and MMP-14 encapsulated in EVs are closely associated with local tumour invasiveness (23). We propose that this molecular signature can be applied to evaluate preoperative tumour staging and define the extent of surgical resection. Second, targeting metastasis-associated proteins carried by EVs to block formation of the pre-metastatic niche provides a viable direction for therapeutic target selection. Breast cancer-derived EVs drive metastatic progression by delivering integrin αvβ3 (24). We posit that clinical intervention targeting integrin αvβ3 can attenuate metastatic dissemination in breast cancer. Meanwhile, inhibiting MMP-14 secretion and enzymatic activity in EVs can effectively reduce ECM remodelling and local infiltration in cervical cancer. Third, engineered EVs can be rationally modified to achieve lesion-specific drug delivery in clinical settings. Integrin αvβ3-functionalised EVs enable precise delivery of therapeutic agents to pulmonary metastatic lesions, enhancing the pulmonary accumulation efficiency of chemotherapeutic drugs while reducing systemic toxic and adverse effects.

Tumour-derived EVs systemically drive tumour invasion and distant metastasis through a three-tiered mechanistic cascade: Integrin-mediated organ targeting, matrix protease-dependent barrier degradation and integrin-ECM synergistically regulated cell migration. Within this regulatory network, integrin subtypes determine the organ specificity of metastatic dissemination. At present, the differential contributions of distinct EV subpopulations to pre-metastatic niche formation remain poorly defined. Meanwhile, whether integrin-mediated EV targeting is modulated by the physical properties of the TME remains under debate. Detection of specific integrin subtypes in circulating EVs can serve as a predictive biomarker for assessing the risk of tumour metastasis. Small EVs (for example, exosomes) primarily reach distant organs via the systemic circulation, mediate organ-specific targeting via membrane-bound integrins and induce pre-metastatic niche establishment. Disrupting the interaction between EV integrins and endothelial cells of target organs holds promise as a novel strategy to inhibit distant tumour metastasis (Fig. 2).

Tumour immune escape is a multifaceted biological process in which malignant cells evade immune recognition and elimination through a range of molecular and cellular mechanisms, thereby supporting their survival, proliferation and metastatic dissemination. As a hallmark of tumour progression and systemic spread, immune escape involves complex interactions between tumour cells and host immune components. Among the most extensively characterised mechanisms is the secretion of EVs by tumour cells, which carry immunosuppressive cargo, including cytokines, checkpoint ligands and regulatory miRNAs, that actively remodels the TME into an immunosuppressive niche, impairing antitumour immunity and enabling immune evasion (25,26).

One of the best-established mechanisms by which tumour cells evade immune surveillance is the activation of immune checkpoint pathways. Among these, programmed death-ligand 1 (PD-L1) is the most extensively characterised immune checkpoint molecule. PD-L1 is frequently endogenously upregulated at the cell surface in multiple human malignancies, such as non-small-cell lung carcinoma, triple-negative breast cancer, gastric adenocarcinoma and cutaneous melanoma. Upon binding to its cognate receptor programmed cell death protein 1 (PD-1) on activated T lymphocytes, PD-L1 triggers intracellular signalling through the immunoreceptor tyrosine-based inhibitory motif and the immunoreceptor tyrosine-based switch motif (ITSM), leading to recruitment and activation of the inhibitory phosphatase Src homology region 2 domain-containing phosphatase-2. This cascade ultimately suppresses T-cell proliferation, reduces cytokine production and induces functional exhaustion (27). Notably, ITSM phosphorylation is enhanced upon PD-1/PD-L1 engagement, thereby amplifying the inhibitory signal.

EVs secreted by tumour cells serve as critical carriers, enabling PD-L1 to exert systemic immunosuppressive effects. Accumulating evidence indicates that EVs derived from multiple malignant tumours, including melanoma and non-small cell lung cancer, can functionally express PD-L1 on their surface. These PD-L1-bearing EVs bind to PD-1 on the surface of T cells, markedly inhibiting CD8+ T-cell activation and proliferation (25). Meanwhile, PD-L1 signalling induces T-cell apoptosis and blocks T-cell receptor signal transduction. In addition to suppressing T-cell activation, PD-L1 inhibits the PI3K/Akt/mTOR signalling pathway and enhances the expression and function of phosphatase and tensin homologue. It also promotes the differentiation of inducible regulatory T cells (Tregs), which secrete TGF-β to further repress effector T-cell function. These cascading regulatory effects collectively establish systemic immunosuppression, thereby facilitating tumour immune evasion (28).

In the indirect pathway, members of the TGF-β protein family predominantly drive the differentiation of CD4+ T cells into Tregs, which exert potent immunosuppressive effects, mainly through the canonical SMAD signalling cascade (29). This pathway is tightly regulated at multiple hierarchical levels, including ubiquitin-mediated proteasomal degradation of SMAD proteins, phosphatase-catalysed dephosphorylation, and competitive inhibition of receptor-regulated SMADs by inhibitory SMADs (30). Notably, TGF-β has a context-dependent dual role in tumourigenesis: it functions predominantly as a tumour suppressor during early carcinogenesis but frequently acquires pro-tumourigenic properties in advanced disease (31).

EVs modulate immune responses through both direct intercellular communication and indirect signalling pathways, primarily by transferring immunoregulatory molecules such as PD-L1 and TGF-β. Advances in clinical detection methods, such as PD-L1 immunohistochemistry, circulating tumour-DNA sequencing and immune-cell profiling (32), have supported the development of a multilayered immunotherapeutic framework and a comprehensive regulatory network governing immune evasion. Collectively, these findings provide mechanistic insights into tumour-induced immunosuppression and immune escape, as well as a translational basis for the clinical implementation of related diagnostic tools and therapeutic interventions. Specifically, tumour-derived EVs synergistically shape local and systemic immunosuppressive microenvironments through two mechanisms: Direct delivery of PD-L1 to suppress effector T-cell function and indirect delivery of TGF-β to induce Treg differentiation. Furthermore, the intrinsic vesicular carrier properties of EVs markedly prolong the duration and expand the spatial range of action of these immunosuppressive molecules.

Nevertheless, the relative contributions of EV-associated PD-L1 and tumour cell surface PD-L1 to immune evasion remain controversial. The active forms of TGF-β and the specific target molecules in EVs from different tumour origins have not been fully elucidated. Meanwhile, circulating EV-associated PD-L1 levels may serve as predictive biomarkers of the therapeutic efficacy of immune checkpoint inhibitors. Bispecific inhibitors simultaneously targeting EV-associated PD-L1 and EV-associated TGF-β may help overcome resistance to single-agent immunotherapy in the future (33) (Fig. 3).

EV-associated pro-angiogenic factors promote tumour angiogenesis. Tumour growth requires the formation of new blood vessels to supply oxygen and nutrients, a process known as tumour angiogenesis (34). Recent studies have shown that tumour-derived EVs are critical mediators of angiogenesis (35). By delivering multiple pro-angiogenic bioactive factors, EVs help establish a tumour endothelial microenvironment that supports angiogenesis (36).

EVs directly initiate angiogenic programmes by enriching and delivering core factors, including VEGF and basic fibroblast growth factor (bFGF) (37). Among the signalling pathways implicated in this process, the VEGF-VEGFR axis is a central regulatory mechanism governing both angiogenesis and tumour progression (38). Tumour-derived EVs selectively enrich and stabilise VEGF, facilitating its targeted delivery to vascular endothelial cells. This interaction activates pro-angiogenic signalling pathways, thereby promoting endothelial cell proliferation, migration and tubule formation, which are key steps in tumour angiogenesis. Clinical and experimental evidence supports this mechanism. For example, glioblastoma-derived EVs markedly increase VEGF levels in cerebrospinal fluid and enhance the in vitro tubulogenesis capacity of human vascular endothelial cells (39).

In addition to VEGF, EVs carry a range of bioactive molecules, including bFGF, platelet-derived growth factor and IL-8 (32). Notably, bFGF binds to its cognate receptor, fibroblast growth factor receptor, to stimulate tumour endothelial cell migration and acts synergistically with VEGF to enhance angiogenesis (40). Furthermore, MMPs packaged within EVs facilitate extracellular matrix degradation, creating permissive microenvironments for neovessel sprouting and stabilisation (36).

EVs enriched in pro-angiogenic factors show an enhanced capacity to stimulate angiogenesis (41). EVs can respond to microenvironmental changes and dynamically modulate the magnitude of angiogenesis. In tumour cells, stress conditions such as hypoxia and oncogene activation upregulate transcription factors, including hypoxia-inducible factor 1α (HIF-1α), leading to increased expression of pro-angiogenic genes such as VEGF and bFGF, thereby altering EV cargo composition (42). Notably, EVs carrying miR-210 suppress key anti-angiogenic regulators, including ephrin-A3, effectively initiating and sustaining the tumour angiogenic switch (43). These molecular mechanisms not only supply tumour cells with essential oxygen and nutrients, but also facilitate local invasion and dissemination into adjacent tissues (44).

This mechanism has substantial translational potential in clinical practice. Clinical evidence indicates that serum EV-associated VEGF levels in patients with colorectal cancer are markedly and positively associated with intratumoural micro vessel density (MVD) scores (45,46). These findings indicate that EV-associated VEGF may serve as a promising non-invasive biomarker for assessing tumour angiogenic activity and predicting patient prognosis, highlighting its potential clinical utility.

From a liquid biopsy perspective, the positive correlation between VEGF levels in serum EVs and tumour tissue MVD suggests that EV-carried VEGF may be useful for evaluating tumour angiogenic status and patient prognosis (47). In therapeutic target screening, the VEGF signalling pathway represents one of the core mechanisms driving tumour neovascularisation (48). Clinical experiments have shown that glioblastoma-derived EVs markedly increase VEGF concentrations in cerebrospinal fluid, exceeding normal levels. Targeting EV-mediated angiogenesis may therefore help overcome resistance induced by conventional anti-VEGF agents. Finally, in the application of engineered EVs, previous studies have shown that EVs loaded with miR-210 can suppress key anti-angiogenic regulators such as ephrin-A3 and effectively trigger the tumour angiogenic switch. Accordingly, miRNAs may be used in engineered EV-based strategies to specifically target tumour endothelial cells (49).

The VEGF signalling pathway constitutes a central regulatory mechanism underlying tumour angiogenesis and is widely recognised as a clinically relevant biomarker in oncology (50,51). Given the pivotal role of VEGF in promoting neovascularisation, therapeutic strategies targeting VEGF or its cognate receptor, VEGFR, have become a major focus in anticancer drug development. Nevertheless, clinical experience indicates that monotherapy based solely on the inhibition of pro-angiogenic factors frequently has limitations, including the development of resistance and suboptimal therapeutic responses.

In conclusion, tumour-derived EVs trigger tumour angiogenesis through a multidimensional cascade involving cytokine activation, extracellular matrix remodelling and hypoxia-induced miRNA regulation, with multiple pro-angiogenic factors encapsulated within EVs exerting synergistic effects. However, the relative contributions of EVs and free pro-angiogenic factors to tumour angiogenesis remain unclear. Moreover, the angiogenic potency of EVs secreted by distinct cell populations requires further systematic investigation. Circulating EV-associated VEGF levels may serve as predictive biomarkers of the therapeutic efficacy of anti-angiogenic agents. Depletion of tumour-derived EVs or functional blockade of their pro-angiogenic cargo represents a novel therapeutic strategy for anti-angiogenic cancer treatment (Fig. 4).

EVs act as central drivers of the horizontal transmission of metabolic reprogramming phenotypes and systematic remodelling of the tissue microenvironment. Metabolic reprogramming is widely recognised as a hallmark of cancer; it not only fuels malignant tumour cell proliferation through systematic rewiring of energy and biosynthetic metabolism, but also contributes to the establishment and maintenance of an immunosuppressive TME. The primary mechanism underlying tumour immune evasion involves the direct suppression of tumour-infiltrating immune cell function through competitive depletion of essential nutrients, including glucose and glutamine, and accumulation of immunosuppressive metabolic by-products, notably lactic acid, ultimately facilitating immune escape and tumour progression (52).

The core mechanism underlying EV-mediated metabolic reprogramming lies in the selective packaging and delivery of a broad panel of key metabolic enzymes regulated by transcription factors. Specifically, activation of key transcriptional regulators, such as HIF-1α and c-Myc, induces the expression of glucose transporter 1 and other membrane transport proteins, thereby markedly increasing cellular glucose uptake and supplying essential carbon substrates for downstream metabolic pathways (53). Subsequently, intracellular glucose is phosphorylated by hexokinase 2 (HK2), an enzyme consistently overexpressed in malignant tumours. This step commits glucose to glycolysis and serves as a critical determinant of glycolytic flux (54). Furthermore, tumour cells preferentially express the M2 isoform of pyruvate kinase (PKM2), which, through its distinct kinetic properties and non-metabolic regulatory functions, synergises with upstream alterations to establish a metabolic configuration conducive to rapid proliferation and biomass accumulation (55).

By simultaneously delivering key downstream metabolic enzymes, EVs function as central executors that drive the cascade amplification of glycolysis and the systemic acidification of the tissue microenvironment (56). Downstream of PKM2, lactate dehydrogenase A (LDHA) is upregulated as a pivotal metabolic enzyme that amplifies glycolytic flux, sustains high-rate glycolysis and drives substantial lactic acid accumulation, thereby providing an essential energetic substrate for rapid tumour cell proliferation (6). Lactic acid is actively exported from tumour cells through monocarboxylate transporters, not only eliminating metabolic waste but also inducing pronounced acidification of the TME. This acidification is not merely a passive by-product of heightened glycolytic activity. Rather, it functions as an active modulator that creates conditions favourable for tumour invasion, metastasis and immune evasion. Specifically, TME acidosis promotes tumour cell migration, local invasion and distant metastasis, while concurrently impairing anti-tumour immunity, most notably by suppressing cytotoxic T lymphocyte function through disruption of T-cell receptor signalling and critical metabolic pathways. Moreover, lactic acid recruits immunosuppressive cell populations, including Tregs and myeloid-derived suppressor cells, thereby reinforcing an immunosuppressive niche that facilitates tumour immune escape (57). This mechanistic framework has been experimentally validated in pancreatic ductal adenocarcinoma, in which pancreatic cancer-derived EVs deliver HK2 to recipient cells, resulting in ~2.5-fold increases in glucose uptake and lactate secretion (58). Collectively, this metabolic reprogramming establishes a localised, persistently acidic TME that critically supports tumour progression and immune evasion.

Regarding translational clinical applications, from a liquid biopsy perspective, HK2 and LDHA expression levels in EVs may serve as biomarkers for tumour metabolic subtyping and guide individualised therapy (59). For instance, patients with pancreatic cancer and high HK2 expression in circulating EVs show a better therapeutic response to glycolysis inhibitors such as 2-deoxyglucose. Meanwhile, serum EV-associated lactate levels may be used to assess TME acidification and predict immunotherapeutic efficacy. In therapeutic target selection, as described above, inhibition of HK2, delivered via pancreatic cancer cell-derived EVs, reduces glucose uptake in recipient cells by 62% and decreases lactate secretion by 71%, while markedly augmenting the activity of tumour-infiltrating T cells. Accordingly, targeting EV-mediated metabolic enzymes represents a viable strategy to abrogate metabolic reprogramming in the TME (60). With respect to engineered EVs, metabolic enzymes including HK2 and LDHA have become critical research targets. EVs loaded with glycolysis inhibitors enable precise targeting of tumour cell metabolic pathways, thereby avoiding systemic metabolic adverse effects. To date, engineered EVs encapsulating LDHA inhibitors have completed preclinical validation in pancreatic cancer models, demonstrating pronounced suppression of tumour growth and prolonged overall survival.

Collectively, these translational and pre-clinical observations highlight the central contribution of EV-packaged metabolic enzymes to tumour progression, prompting further mechanistic dissection of how tumour-derived EVs propagate metabolic reprogramming across the tumour microenvironment.

The aforementioned studies demonstrate that key metabolic enzymes, particularly HK2 and LDHA, serve as core functional cargos of tumour-derived EVs and play pivotal roles in EV-mediated intercellular transmission of metabolic reprogramming by modulating cellular energy metabolism. Mediated by tumour-derived EVs, this metabolic reprogramming, notably characterised by enhanced glycolytic flux and increased lactate secretion, extends from individual tumour cells to the entire tissue niche, establishing a mechanistically coherent pathogenic axis linking intracellular metabolic alterations to systemic remodelling of the TME. This reprogramming exerts dual biological effects: First, it supplies the bioenergetic and biosynthetic substrates required for rapid tumour cell proliferation; second, it fosters an immunosuppressive TME through extracellular acidification, thereby facilitating immune evasion, a hallmark of malignant progression. Consequently, blocking the EV-mediated intercellular transfer of key metabolic enzymes, such as HK2 and LDHA, has emerged as a promising therapeutic strategy that can simultaneously suppress tumour metabolic reprogramming and the formation of an immunosuppressive microenvironment, exert dual anti-tumour effects, and offer novel mechanistic insights and potential avenues for clinical intervention in malignant tumours (Fig. 5).

Multidrug resistance (MDR) in cancer markedly undermines the efficacy of clinical anticancer therapies (61). Accumulating evidence indicates that EVs, as critical vehicles for intercellular communication among tumour cells, contribute to MDR through multiple molecular mechanisms. Among these, multidrug resistance protein 1 (P-glycoprotein) has a central mechanistic role.

P-gp, a drug-resistance-associated transmembrane transporter, plays a pivotal role in mediating MDR in malignant tumours. Overexpression or hyperactivation of P-gp in tumour cells confers a survival advantage under chemotherapeutic pressure by facilitating the ATP-dependent efflux of diverse anticancer agents, thereby reducing intracellular drug accumulation and diminishing therapeutic efficacy (62). Furthermore, EVs secreted by drug-resistant tumour cells frequently exhibit elevated surface expression of clinically relevant biomarkers, including HER2 and CD20, that mirror those on the parental tumour cell membrane (63). In the context of targeted therapies such as trastuzumab (anti-HER2) and rituximab (anti-CD20), these EVs act as molecular decoys by competitively binding therapeutic antibodies, sequestering drug molecules and consequently lowering the bioavailable concentration of active drug reaching tumour cells, ultimately contributing to therapeutic resistance and clinical treatment failure (64).

The ABC transporter family represents a well-established molecular mechanism underlying MDR. Proteomic profiling has demonstrated notable upregulation of three key ABC transporters, ABCB1 (P-gp/MDR1), ABCC1 (MRP1) and ABCG2 (BCRP), in EVs isolated from drug-resistant tumours (65,66). These membrane-bound efflux pumps use energy derived from ATP hydrolysis to actively export chemotherapeutic agents from cells, thereby substantially diminishing intracellular drug accumulation and compromising therapeutic efficacy. Notably, MDR1 expression in EVs derived from paclitaxel-resistant ovarian cancer cell lines was ~5.8-fold higher than that observed in their drug-sensitive counterparts (67).

Moreover, EVs can deliver DNA damage repair-associated proteins, including topoisomerase IIα (TOP2A), to recipient cells. TOP2A is a critical regulator of DNA replication and cell proliferation, with enzymatic activity tightly coordinated with cell cycle progression. The expression of TOP2A peaks during the G₂/M phase and declines rapidly after mitotic completion (68,69). Recent evidence has demonstrated that EV-mediated transfer of TOP2A disrupts canonical DNA damage repair mechanisms and confers a 3- to 4-fold increase in cisplatin resistance in HeLa cells (70).

Regarding clinical translational applications, for liquid biopsy biomarkers, as noted in previous studies, high preoperative serum EV expression of MDR1 in patients with ovarian cancer indicates a 5.8-fold elevated risk of paclitaxel resistance (71). EV-associated TOP2A levels can be used to predict the therapeutic response to cisplatin and guide the selection of postoperative adjuvant chemotherapy regimens (72). Targeting drug resistance-related proteins carried by EVs can reverse tumour therapeutic resistance. Combined administration of MDR1 inhibitors and EV-depletion agents increases intracellular paclitaxel concentration in drug-resistant ovarian cancer cells by 3.5-fold and restores chemosensitivity (73). Blocking EV-mediated intercellular transfer of TOP2A enhances the antitumour activity of cisplatin by 3- to 4-fold. For engineered EV applications, EVs loaded with drug resistance-reversing small interfering RNAs can specifically deliver gene-silencing molecules that target drug resistance (74). In multidrug-resistant breast cancer models, this strategy restores tumour cell sensitivity to doxorubicin to the level observed in drug-sensitive cell lines (75).

In summary, from our perspective, drug resistance-associated proteins collectively contribute to tumour treatment resistance through multiple interconnected mechanisms, including pre-emptive drug binding, active efflux of chemotherapeutic agents and disruption of DNA repair pathways. These mechanisms establish a functional link between EV-mediated drug resistance and clinical treatment outcomes, positioning EVs as critical biomolecular carriers for investigating tumour drug resistance. Furthermore, they provide promising avenues for developing strategies to reverse resistance and optimise therapeutic regimens. Tumour-derived EVs confer therapeutic resistance via drug resistance proteins through drug binding, chemotherapeutic efflux and DNA repair disruption. However, the actual contribution of EV-mediated transmission of drug resistance to clinical tumour drug resistance remains unclear. Relevant studies remain limited, clinical data are insufficient and differences in transmission efficiency among distinct EV subpopulations during the propagation of drug resistance have not been fully elucidated. Detection of drug resistance-related protein expression levels in circulating EVs enables early prediction of tumour therapeutic response. The combined application of EV-depletion agents and conventional targeted agents is expected to overcome tumour drug resistance and improve therapeutic efficacy (Fig. 6; Table II).

Exosomes serve as promising biological biomarkers for liquid biopsy, exhibiting well-documented clinical utility in tumour screening and adjunctive diagnosis, progressing steadily from foundational research toward integration into clinical decision-making frameworks.

Liquid biopsy platforms leveraging exosome-associated proteins demonstrate superior analytical sensitivity and specificity. Notably, immune checkpoint molecules, including PD-L1, which is consistently overexpressed on tumour-derived exosomes, represent robust and clinically relevant detection targets (76).

Substantial clinical evidence substantiates the high diagnostic accuracy of exosome-based assays in prostate cancer detection. It is estimated that implementation of this technology could reduce unnecessary prostate biopsies by ~26%, thereby mitigating patient discomfort and minimizing wastage of healthcare resources associated with invasive procedures (77). This underscores the transformative potential of exosome-based liquid biopsy as a dynamic, non-invasive monitoring modality.

Exosomes function not merely as passive biomarkers but also as active therapeutic delivery vehicles and mechanistically relevant intervention targets. Their clinical translation is now advancing into the validation phase, particularly in addressing tumour drug resistance and improving therapeutic efficacy.

Exosomes engineered via surface conjugation of targeting ligands, such as EGFR-specific single-chain variable fragments, demonstrate markedly enhanced accumulation at tumour sites (78). This strategy offers a structurally grounded solution to two longstanding challenges in oncology: Suboptimal target specificity and dose-limiting systemic toxicity associated with conventional chemotherapeutics.

Dual-targeting exosome-based inhibitors co-blocking PD-L1 and TGF-β have progressed to phase II clinical trial stage (79). Interim data indicate a ~38% reduction in the incidence of resistance to immune checkpoint blockade therapy (80). These findings substantiate that exosomes are not only integral components of resistance pathways but also promising, mechanism-informed therapeutic levers for overcoming immune evasion and reversing treatment resistance.

Although exosomes hold considerable promise for clinical applications, their translation from laboratory research to large-scale clinical implementation is hindered by stringent industrial quality control requirements, constituting a critical bottleneck in their clinical translation.