Siglec Ligand Profiling on Extracellular Vesicles Reveals a Cancer‐Related Signature with Immunosuppressive Function in Pancreatic Cancer

Cancer-derived extracellular vesicles (EVs) act as systemic carriers of functional sialic acids and participate in local or distant immune escape via the Siglec pathway. Therefore, assessing the expression of Siglec ligands on EVs can facilitate the exploration of novel cancer biomarkers and enable the evaluation of circulating sialic acid-mediated immunosuppression. However, the structural complexity and functional redundancy of Siglec ligands pose challenges for evaluating their collective role in immune evasion. Here, an adjustable Siglec-DNA barcoding platform is established for multiplexed detection of four Siglec ligands on EVs, thereby enabling the simultaneous profiling of multiple ligand-receptor pairs in a single competitive assay. EV Siglec ligand signatures show statistical differences between cancer and normal groups, as quantified by the Siglec-DNA platform in cell lines and clinical samples, highlighting their potential for pancreatic cancer discrimination. Specific types of Siglec ligands on EVs also inactivate natural killer (NK) cells and T cells in co-culture, demonstrating their immunosuppressive potential. These findings uncover a novel, systemic mechanism of immune inhibition mediated by sialic acids, and also offer new insights into how EVs modulate cancer immunity.