Pancreatic cancer cell-derived microRNA-155-5p-containing extracellular vesicles promote immune evasion by triggering EHF-dependent activation of Akt/NF-κB signaling pathway

Abstract

Pancreatic cancer (PC)-derived EVs have been extensively investigated due to their promising potential as disease biomarkers for diagnosis, monitoring, and treatment decisionmaking. Herein, we explored the mechanism underlying PC-derived EVs in immune evasion of PC. Initially, microRNA (miR)-155-5p level was quantified by RT-qPCR in tumor tissue samples from PC patients, EVs isolated from PC cell lines and PC cell lines. Then, the interaction between miR-155-5p and EHF was identified using dual-luciferase reporter assay. Ectopic expression and knockdown experiments were conducted in PC cells, PC cells-derived EVs, or mouse xenograft model of PC. Afterwards, cell invasion, proportion of macrophage and immune cell subsets, and expression of NF-κB signaling-related genes were assessed using Transwell assay, flow cytometry, RT-qPCR and western blot analysis, respectively. Accordingly, miR-155-5p was upregulated in clinical tissue samples, Pan02-derived EVs and PC cell lines. miR-155-5p knockdown in PC cells enhanced anti-tumor immunity. PC cell-derived EVs facilitated immunosuppressive microenvironment by promoting T cell depletion. In addition, PC cell-derived EVs transferred miR-155-5p to macrophages and then promoted polarization of macrophages to M2 phenotype. EHF was downregulated in PC and could be targeted by miR-155-5p, which resulted in the activation of the Akt/NF-κB signaling. Our findings revealed a previously unrecognized tumor immune evasion-promoting function of PC-derived EV miR-155-5p in PC development by suppressing EHF and activating NF-κB signaling. This study suggested that the miR-155-5p/EHF/Akt/NF-κB axis can be exploited to prevent cancer immune evasion triggered by therapies.