LAUSR

Over the past 15 years, several biological and pathological characteristics proved their significance in pediatric anaplastic lymphoma kinase (ALK)-positive anaplastic large-cell lymphoma (ALCL) prognostic stratification. However, the identification of new non-invasive disease biomarkers, relying on the most important disease mechanisms, is still necessary. In recent years, plasmatic circulating small extracellular vesicles (S-EVs) gathered great importance both as stable biomarker carriers and active players in tumorigenesis. In the present work, we performed a comprehensive study on the proteomic composition of plasmatic S-EVs of pediatric ALCL patients compared to healthy donors (HDs). By using a mass spectrometry-based proteomics approach, we identified 50 proteins significantly overrepresented in S-EVs of ALCL patients. Gene Ontology enrichment analysis disclosed cellular components and molecular functions connected with S-EV origin and vesicular trafficking, whereas cell adhesion, glycosaminoglycan metabolic process, extracellular matrix organization, collagen fibril organization and acute phase response were the most enriched biological processes. Of importance, consistently with the presence of nucleophosmin (NPM)-ALK fusion protein in ALCL cells, a topological enrichment analysis based on Reactome- and Kyoto Encyclopedia of Genes and Genomes (KEGG)-derived networks highlighted a dramatic increase in proteins of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway in ALCL S-EVs, which included heat shock protein 90-kDa isoform alpha 1 (HSP90AA1), osteopontin (SPP1/OPN) and tenascin C (TNC). These results were validated by Western blotting analysis on a panel of ALCL and HD cases. Further research is warranted to better define the role of these S-EV proteins as diagnostic and, possibly, prognostic parameters at diagnosis and for ALCL disease monitoring.