Small and Large Extracellular Vesicles Derived from Pleural Mesothelioma Cell Lines Offer Biomarker Potential

Simple Summary Pleural mesothelioma, a fatal thoracic cancer with one of the poorest survival rates of any cancer, is in urgent clinical need for biomarkers to aid early diagnosis, improve prognostication, and treatment options. Extracellular vesicles (EVs) have great potential as tumour biomarkers, however there are limited studies so far on their role in mesothelioma. We aimed to characterize different classes of EV derived from different mesothelioma cell lines. We provided a comprehensive proteomic database of cancer associated proteins in EVs that can offer new targets for future biomarker studies in pleural mesothelioma. We have also demonstrated that different subtypes of EVs can be isolated, namely 10 K, 18 K, and 100 K, each carrying oncogenic cargo with biomarker potential for pleural mesothelioma. Major differences were found in the cargo between the three EV subtypes, which can help narrow the molecular targets for diagnostic, prognostic, and predictive biomarker studies. Pleural mesothelioma, previously known as malignant pleural mesothelioma, is an aggressive and fatal cancer of the pleura, with one of the poorest survival rates. Pleural mesothelioma is in urgent clinical need for biomarkers to aid early diagnosis, improve prognostication, and stratify patients for treatment. Extracellular vesicles (EVs) have great potential as biomarkers; however, there are limited studies to date on their role in pleural mesothelioma. We conducted a comprehensive proteomic analysis on different EV populations derived from five pleural mesothelioma cell lines and an immortalized control cell line. We characterized three subtypes of EVs (10 K, 18 K, and 100 K), and identified a total of 4054 unique proteins. Major differences were found in the cargo between the three EV subtypes. We show that 10 K EVs were enriched in mitochondrial components and metabolic processes, while 18 K and 100 K EVs were enriched in endoplasmic reticulum stress. We found 46 new cancer-associated proteins for pleural mesothelioma, and the presence of mesothelin and PD-L1/PD-L2 enriched in 100 K and 10 K EV, respectively. We demonstrate that different EV populations derived from pleural mesothelioma cells have unique cancer-specific proteomes and carry oncogenic cargo, which could offer a novel means to extract biomarkers of interest for pleural mesothelioma from liquid biopsies.