Gastric cancer-derived extracellular vesicles enriched with microRNA-675-3p contribute to the MAPK/PD-L1-mediated tumor immune escape by targeting CXXC4

Abstract microRNAs (miRs) delivered by gastric cancer (GC)-secreted extracellular vesicles (GC-EVs) are associated with the immune escape in GC. Microarray analysis based on the GSE112369 dataset identified the presence of poorly expressed CXXC finger protein 4 (CXXC4) in GC, which was validated in clinical samples of GC patients. Moreover, prediction based on TargetScan analysis demonstrated putative miR-675-3p binding site in the 3’UTR region of CXXC4. Thereby, our study aims to determine the role of GC-EV-encapsulated miR-675-3p in GC. Firstly, CXXC4 was found to be negatively correlated with PD-L1. The effects of mitogen-activated protein kinases (MAPK) signaling on GC were evaluated using activator of the MAPK pathway. The overexpression of CXXC4 led to downregulated MAPK signaling pathway, thus decreasing PD-L1 expression to augment the proliferation and activation of T cells co-cultured with GC cell HGC-27. GC-EV-encapsulated miR-675-3p negatively regulated the expression of its target gene CXXC4. GC-EV-encapsulated miR-675-3p increased PD-L1 expression to stimulate the immune escape in vitro and EV-encapsulated miR-675-3p accelerated cisplatin resistance in vivo. Collectively, the aforementioned findings present a mechanism in which EV-mediated miR-675-3p upregulates PD-L1 expression, promoting immune escape in GC.