Isolation and characterizataion of prostate-derived extracellular vesicles as a liquid biopsy strategy in cancer diagnosis

Introduction: In the past years, extracellular vesicles (EVs) have attracted considerable interest due to their ability to provide valuable diagnostic information from liquid biopsies. The high abundance in all bodily fluids and their cargo stability confers EVs the potential as a powerful tool to not only obtain novel biomarkers from inaccessible tissues, therapy response and monitoring, but also to reduce infection risks of conventional highly invasive biopsies. Virtually all cells continuously release vesicles into the extracellular environment, diverse in size, content and features depending on the biogenesis, origin and function. This heterogeneity adds a layer of complexity when attempting to isolate and characterize tissue-specific vesicles. Methods: Hence, we aimed to use a immunomagnetic capture approach for prostate-derived EVs from cell culture supernatants, with further investigation into human plasma and urine samples. Analysis was performed by nanoparticle tracking analysis, western blotting and electron microscopy. Additionally, an in-house spotted antibody micro array is in development. Here, we intend to detect different EV sub-populations based on their surface markers. Results: Isolated immunocaptured EV populations based on the classical EV marker CD9 show an increased signal for the luminal protein TSG101. EV populations targeting the tissue-specific marker prostate specific membrane antigen (PSMA), were found positive for TSG101 in a lower extent indicating a sub-population of EVs. The microarray uses less than100 µL of sample (concentrated cell culture supernatant, human plasma, urine) and leads to a faster characterization within 3 h for EV surface marker as compared to western blot. Summary/Conclusion: Immunomagnetic isolation might be a promising approach for liquid biopsy and thereby the microarray could be valuable to identify potential capture targets. The current design for 6different surface marker from 16 samples simultaneously could be easily extended for sample size and surface profiling allowing for a more economical way to multiplex samples.