The review lays out the biogenesis of exosomes as a highly regulated, multi-step assembly line. It begins with the formation of early endosomes and the sorting of cargo, followed by the generation of intraluminal vesicles, or ILVs, which bud into the interior of the endosome. As the endosome matures into a multivesicular body, or MVB, it is transported through the cytoplasm and ultimately fuses with the plasma membrane, releasing its ILVs into the extracellular space as exosomes. Each of these stages depends on specific protein machinery: the ESCRT complexes and tetraspanins such as CD63, CD9, and CD81 drive MVB formation, Rab GTPases steer MVB transport, the ceramide pathway contributes to secretion, and integrins and heparan sulfate proteoglycans mediate uptake by target cells. What the review emphasizes is that none of this machinery operates independently of PTMs.

Ubiquitination, the attachment of the small protein ubiquitin to target proteins, emerges as a central player in cargo selection. The classic ESCRT-dependent sorting pathway relies on ubiquitinated cargo being recognized by ESCRT components such as hepatocyte growth factor-regulated tyrosine kinase substrate, or HRS, tumor susceptibility gene 101, or TSG101, and ALG-2 interacting protein X, known as ALIX. By tagging specific proteins with ubiquitin, cells effectively decide which molecular messages get packed into exosomes and which are left behind or degraded. The review highlights how enzymes such as ring finger protein 16, or RNF167, participate in this sorting process, and how perturbing ubiquitination can reshape the entire cargo profile of released vesicles, with downstream consequences for how tumor cells communicate with their environment.

Phosphorylation, the addition of phosphate groups by kinases, adds another layer of control. The review describes how phosphorylation events modulate the activity of RNA-binding proteins such as heterogeneous nuclear ribonucleoprotein A2B1 and Y-box binding protein 1, both of which help load microRNAs and other RNA species into exosomes. Casein kinase 2 and focal adhesion kinase are among the kinases implicated in regulating vesicle formation and release. Hypoxia-inducible factors, which accumulate when tumor cells are starved of oxygen, intersect with phosphorylation-driven signaling to alter the composition and quantity of vesicles secreted under hypoxic conditions, a hallmark of the tumor microenvironment. In this way, phosphorylation links the metabolic and stress state of a cancer cell directly to the messages it broadcasts through sEVs.

Acetylation and SUMOylation, the attachment of acetyl groups and small ubiquitin-like modifier proteins respectively, round out the PTM network. The review explains that these modifications influence the stability, localization, and interaction partners of key sorting factors, including members of the ESCRT machinery and the vacuolar protein sorting protein VPS4, which provides the energy for membrane scission during ILV formation. SUMOylation of RNA-binding proteins can alter which RNA cargo is selected for packaging, while acetylation states of chaperone proteins such as heat shock protein 70 and heat shock protein 90 affect their role in stabilizing vesicle contents. The authors argue that these modifications form an integrated regulatory web rather than isolated switches, meaning that therapeutic manipulation of one PTM pathway will inevitably ripple through the entire sEV production system.

The consequences for cancer progression are profound. The review systematically connects PTM-regulated sEV biology to tumor growth, immune modulation, and metastasis. Exosomes released by tumor cells can reprogram recipient cells to promote epithelial-mesenchymal transition, the process by which cancer cells acquire migratory and invasive properties. Vesicle cargo influenced by PTMs includes proteins such as CUB domain-containing protein 1 and galectin-3 binding protein, which have been linked to metastatic behavior in cancers including breast cancer, hepatocellular carcinoma, pancreatic ductal adenocarcinoma, glioblastoma, non-small cell lung cancer, and oral squamous cell carcinoma. Because the cargo composition is itself PTM-dependent, the chemical state of the producing cell ultimately determines how aggressive the resulting intercellular signals will be.

Immune modulation represents another critical frontier. The review describes how sEVs carry molecules such as Fas ligand that can induce apoptosis in immune cells, and how vesicle-mediated signaling contributes to the expansion and activation of myeloid-derived suppressor cells, which dampen antitumor immunity. Granulocyte colony-stimulating factor signaling and the activity of the mammalian target of rapamycin complex 1, or mTORC1, intersect with PTM pathways to shape the immunosuppressive cargo of tumor-derived vesicles. Understanding which PTMs control the loading of immunomodulatory molecules could allow researchers to intervene at the source, potentially stripping tumor exosomes of their ability to blind the immune system or even engineering vesicles that stimulate immune responses against the tumor instead.

These mechanistic insights feed directly into therapeutic applications, which the review examines in depth. The most prominent of these is the use of sEVs as drug delivery vehicles. Because exosomes are naturally biocompatible, cross biological barriers, and can be engineered to display targeting ligands, they are attractive candidates for delivering chemotherapy agents, RNA therapeutics, and CRISPR-based tools to tumors while sparing healthy tissue. The review suggests that manipulating the PTM machinery of producer cells could allow manufacturers to customize vesicle cargo and surface composition, improving delivery efficiency and specificity. Similarly, PTM-informed engineering could enhance the loading of immunotherapeutic payloads, positioning sEVs as versatile platforms for cancer immunotherapy.

Diagnostic applications form a third pillar. The molecular signatures carried by sEVs in blood and other body fluids make them promising liquid biopsy biomarkers, capable of reporting on a tumor’s molecular state without invasive procedures. The review notes that PTM patterns on vesicle proteins could themselves serve as biomarkers, reflecting the signaling state of the originating tumor. It also touches on the technical challenges of the field, including the need for standardized isolation methods such as size-exclusion chromatography and ultracentrifugation, and the importance of community guidelines such as the International Society for Extracellular Vesicles’ minimal information for studies of extracellular vesicles framework, which aims to ensure that findings from different laboratories can be compared reliably.

The authors conclude that a comprehensive understanding of PTM-mediated sEV regulation will open new avenues for targeted therapeutic strategies and precision medicine approaches in cancer treatment. By mapping how ubiquitination, phosphorylation, acetylation, and SUMOylation converge on the molecular machinery of vesicle biogenesis, the review provides a framework for the next generation of experiments: identifying which specific PTM events drive which pathological vesicle signals in which cancers, and then designing drugs or engineering strategies to intervene. The work, supported by the Natural Science Foundation of Ningbo, the National Natural Science Foundation of China, the Natural Science Foundation of Zhejiang Province, and the K.C. Wong Magna Fund at Ningbo University, arrives as interest in extracellular vesicles surges across oncology, and it makes a compelling case that the smallest chemical tags on proteins may hold some of the biggest clues to controlling how cancer communicates, spreads, and evades treatment.

Subject of Research: Post-translational modification control of small extracellular vesicle biology and its therapeutic applications in cancer

Article Title: Post-translational modifications in sEV biology: mechanisms and therapeutic applications in cancer

Article References: Li, Y., Chai, L., Yuan, Z., Chen, J., & Jin, X. (2026). Post-translational modifications in sEV biology: mechanisms and therapeutic applications in cancer. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-08989-z

Image Credits: AI Generated

DOI: 10.1186/s12967-026-08989-z

Keywords: small extracellular vesicles, exosomes, post-translational modifications, ubiquitination, phosphorylation, SUMOylation, cancer, drug delivery, biomarkers, immunotherapy, tumor microenvironment, metastasis