Oncogenic small extracellular vesicles enriched in sphingosine-1-phosphate play a crucial role in pancreatic cancer progression

Small extracellular vesicles (sEVs) from tumour cells mediate intercellular communication and signalling to regulate the progression of pancreatic ductal adenocarcinoma (PDAC). While we and others have shown that PDAC-derived sEVs comprise oncogenic protein and nucleic acid cargo, understanding the lipid landscape of these sEVs remains unknown. Lipids influence both the composition of sEVs and their roles in lipid metabolism and signalling pathways within the tumour microenvironment and tumorigenesis. We hypothesised that specific lipids in oncogenic sEVs might provide insights into PDAC. Comprehensive mass spectrometry-based lipidomic analysis was performed using liquid chromatography-electrospray ionisation-tandem mass spectrometry on sEVs isolated from PDAC and non-malignant pancreatic cell lines, patient-derived xenograft cell lines and plasma from the PDAC transgenic mouse model KPC (KRASWT/G12D/ TP53WT/R172H/Pdx1-Cre+/+). The sEV lipidomic analyses identified over 700 lipid species from 25 lipid classes and subclasses. Our results showed that, compared to non-malignant cells, PDAC-derived sEVs were enriched in specific lysophospholipids, particularly sphingosine-1-phosphate (S1P), a lipid known for its pivotal role in cancer pathogenesis. S1P enrichment was validated in plasma-derived sEVs from KPC mice compared to WT. To explore the functional implications of S1P enrichment, we conducted assays demonstrating that S1P in sEVs facilitated tubule formation in human microvascular endothelial cells and promoted cancer-associated fibroblast cell migration. We show that PDAC-derived sEVs are differentially enriched in specific lipids associated with cancer phenotype. Our findings highlight that PDAC-derived sEVs are enriched in specific lipids, particularly S1P, which plays a crucial role in promoting cancer progression.