Liquid Biopsies and Extracellular Vesicles
Cancer diagnosis has long relied on tissue biopsies, an invasive, often painful, and sometimes risky procedure that captures only a snapshot of tumour biology at a single site. Liquid biopsies are rapidly changing that. By analysing tumour-derived material circulating in blood, urine, or other body fluids, they offer a minimally invasive window into cancer biology in real time. Among the various analytes being explored, including circulating tumour cells (CTCs) and cell-free DNA (cfDNA), extracellular vesicles (EVs) are emerging as particularly compelling biomarker candidates.
What Are Extracellular Vesicles?
EVs are nanosized, membrane-bound particles secreted by virtually all cell types into the extracellular environment. They encompass several subclasses: small EVs (sEVs) including exosomes (typically 30-150 nm, formed through endosomal pathways), microvesicles (100-1000 nm, shed directly from the plasma membrane), and apoptotic bodies, which are larger particles released during programmed cell death. Their lipid bilayer membrane encapsulates a rich cargo of proteins, nucleic acids (mRNA, miRNA, DNA), and lipids that faithfully reflect the biological state of their parent cells. Critically, this membrane protects the cargo from enzymatic degradation in the extracellular environment, preserving its diagnostic integrity.
Why EVs for Cancer Detection?
EVs have shown high accuracy and sensitivity in early cancer detection, classification, and treatment evaluation, making them valuable as a source of biomarkers. They carry stable and representative molecular components, including proteins, nucleic acids, and lipids, enhancing their clinical utility. Journal of Hematology & Oncology
This stability gives EVs a practical advantage over circulating cell-free DNA, which is notoriously fragile and present at very low concentrations in early-stage disease. Small EVs and circulating tumour DNA are both essential components of liquid biopsies used in cancer diagnostics and prognostications, though small EVs offer several advantages over ctDNA. PubMed Central These include their abundance in circulation, the breadth of molecular information they carry, and their capacity to reflect tumour heterogeneity more comprehensively than DNA alone.
Tumour cells release EVs at elevated rates compared with normal cells, and these tumour-derived vesicles carry oncogenic proteins, mutant DNA, and dysregulated miRNAs that can serve as highly specific disease signatures. EVs can transport bioactive cargo to distant sites and facilitate intercellular communication, PubMed Central which means they are not merely passive biomarkers but active participants in tumour biology.
The Diagnostic Landscape
EV-based liquid biopsies are being investigated across a wide spectrum of cancers. At the AACR Annual Meeting 2024, groundbreaking EV-based liquid biopsy studies showcased promising strides in early detection and diagnosis of various cancers, including breast cancer, high-grade serous ovarian cancer, pancreatic ductal adenocarcinoma, colorectal cancer, head and neck cancer, neuroblastoma, and retinoblastoma. PubMed
In lung cancer, one of the deadliest malignancies globally, current studies indicate that the search for biomarkers is increasingly focused on the contents of EVs, particularly miRNAs and lncRNAs, for detecting lung cancer at an early stage. Exosomal miRNAs have demonstrated potential in reducing false-positive rates when used alongside other diagnostic methods, such as low-dose CT scans. MDPI
Protein biomarkers carried by EVs are also proving informative. Studies have reported elevated levels of tumour-associated proteins in EV fractions from patients with bladder cancer (TACSTD2 in urinary exosomes), ovarian cancer (EpCAM and CD24 in ascites-derived EVs), and melanoma (including HSP70, HSP90 isoforms, and the MET oncoprotein in plasma exosomes).
A 2025 study in Nature Communications demonstrated a new dimension of EV diagnostics by profiling DNA methylation patterns within EV-derived DNA. Researchers applied a novel bisulfite-free whole-genome profiling method to EV-DNA from 58 gastric cancer and polyp samples, generating methylomes from sub-nanogram inputs and identifying differentially methylated regions that distinguish cancer from controls. Nature Communications This opens the door to epigenetic liquid biopsy using EVs, a powerful complement to genetic and proteomic analyses.
The Role of AI and Advanced Technologies
Processing the complex, multidimensional datasets generated by EV profiling demands significant computational power. Machine learning is increasingly being applied to integrate EV protein, miRNA, and DNA signatures into predictive diagnostic models, improving classification accuracy and enabling multi-cancer early detection from a single blood draw. Microfluidic platforms are similarly transforming EV isolation and analysis, enabling high-throughput, reproducible processing from small sample volumes that is essential for clinical translation.
Challenges and the Road Ahead
Significant hurdles remain. Standardisation of EV isolation methods is a persistent issue, with ultracentrifugation, size-exclusion chromatography, and precipitation-based approaches each yielding populations of varying purity. The MISEV2023 guidelines from the International Society for Extracellular Vesicles provide an important framework, but clinical adoption requires scalable and cost-effective workflows. Distinguishing tumour-derived EVs from the background noise of EVs shed by healthy cells also remains technically demanding, particularly in early-stage disease where the tumour signal is dilute.
The momentum behind this field is nonetheless considerable. EV-based liquid biopsies have real potential to enable earlier cancer detection when tumours are most treatable, to support non-invasive monitoring of treatment response, and to identify resistance mechanisms as they emerge. As the science matures, EVs look increasingly likely to become a routine part of precision oncology.
IMAGE Circulating EVs CREDIT Shutterstock
Learn more about powerful technologies that are enabling research:
