Proteomic analysis of circulating small extracellular vesicles unique to cervical cancer

Extracellular Vesicles

Background Small extracellular vesicles (sEVs) are membrane vesicles released by healthy and malignant cells. sEVs are potential biomarkers for cancer diagnosis. Cervical cancer (CC) is the fourth most common cancer in females worldwide. Existing biomarkers, such as squamous cell carcinoma antigens, show low specificity. Hence, a novel biomarker for the diagnosis of CC is required. This study aimed to identify potential candidates in sEVs through proteomic analysis for the diagnosis of CC and to determine the EV protein profile to distinguish between healthy and CC serum samples. Methods The number and size distribution of sEVs in healthy controls (HC) and CC were measured using nanoparticle tracking analysis. Differential ultracentrifugation combined with size-exclusion chromatography was used to isolate and purify sEVs derived from the serum of HC and CC. The isolated sEVs were characterized using western blotting and transmission electron microscopy. Liquid chromatography-tandem mass spectrometry was used to identify and compare the protein profiles between CC and HC. EV proteins were validated using the TCGA database. Results The particle concentration in CC was marginally higher than that in HC. The mode size of the particles in CC was significantly smaller than that in the HC-derived particles. Proteomic and functional protein analyses revealed a difference in the EV protein profiles between HC and CC. We found three and 18 uniquely expressed proteins in HC and CC, respectively. Unique EV proteins in CC are involved in angiogenesis and the Ras, VEGF, and FAS signaling pathways, while EV proteins in HC are involved in cellular homeostasis. EV proteins such as C1QB, MYO3B, and NADSYN1 were significantly upregulated in CC and primary tumor tissues, whereas MAFK, OR13C9, PIK3C2, PLCB4, RAB12, and VIP were downregulated in CC sEVs and primary tumor tissues. Conclusion Our study provides useful insights into the potential of sEVs as noninvasive biomarkers for CC diagnosis. Validation with a well-designed cohort should be performed to assure the clinical diagnostic value of specific protein markers for CC sEVs.

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Cigarette smoke (CS) represents one of the most relevant environmental risk factors for several chronic pathologies. Tissue damage caused by CS exposure is mediated, at least in part, by oxidative stress induced by its toxic and pro-oxidant components. Evidence demonstrates that extracellular vesicles (EVs) released by various cell types exposed to CS extract (CSE) are characterized by altered biochemical cargo and gained pathological properties. In the present study, we evaluated the content of oxidized proteins and phospholipid fatty acid profiles of EVs released by human bronchial epithelial BEAS-2B cells treated with CSE. This specific molecular characterization has hitherto not been performed. After confirmation that CSE reduces viability of BEAS-2B cells and elevates intracellular ROS levels, in a dose-dependent manner, we demonstrated that 24 h exposure at 1% CSE, a concentration that only slight modifies cell viability but increases ROS levels, was able to increase carbonylated protein levels in cells and released EVs. The release of oxidatively modified proteins via EVs might represent a mechanism used by cells to remove toxic proteins in order to avoid their intracellular overloading. Moreover, 1% CSE induced only few changes in the fatty acid asset in BEAS-2B cell membrane phospholipids, whereas several rearrangements were observed in EVs released by CSE-treated cells. The impact of changes in acyl chain composition of CSE-EVs accounted for the increased saturation levels of phospholipids, a membrane parameter that might influence EV stability, uptake and, at least in part, EV-mediated biological effects. The present in vitro study adds new information concerning the biochemical composition of CSE-related EVs, useful to predict their biological effects on target cells. Furthermore, the information regarding the presence of oxidized proteins and the specific membrane features of CSE-related EVs can be useful to define the utilization of circulating EVs as marker for diagnosing of CS-induced lung damage and/or CS-related diseases.

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