Proteomic and phosphoproteomic profiling of urinary small extracellular vesicles in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most prevalent form of primary liver cancer and a major cause of cancer-related mortality worldwide. Small extracellular vesicles (sEVs) are heterogeneous populations of membrane-structured vesicles that can be found in many biological fluids and are currently considered as a potential source of disease-associated biomarkers for diagnosis. The purpose of this study was to define the proteomic and phosphoproteomic landscape of urinary sEVs in patients with HCC. Mass spectrometry-based methods were used to detect the global proteome and phosphoproteome profiles of sEVs isolated by differential ultracentrifugation. Label-free quantitation analysis showed that 348 differentially expressed proteins (DEPs) and 548 differentially expressed phosphoproteins (DEPPs) were identified in the HCC group. Among them, multiple phosphoproteins related to HCC, including HSP90AA1, IQGAP1, MTOR, and PRKCA, were shown to be upregulated in the HCC group. Pathway enrichment analysis indicated that the upregulated DEPPs participate in the regulation of autophagy, proteoglycans in cancer, and the MAPK/mTOR/Rap1 signaling pathway. Furthermore, kinase-substrate enrichment analysis revealed activation of MTOR, AKT1, MAP2Ks, and MAPKs family kinases in HCC-derived sEVs, indicating that dysregulation of the MAPK and mTOR signaling pathways may be the primary sEV-mediated molecular mechanisms involved in the development and progression of HCC. This study demonstrated that urinary sEVs are enriched in proteomic and phosphoproteomic signatures that could be further explored for their potential use in early HCC diagnostic and therapeutic applications.