Molecular Mechanisms of Neutrophil Extracellular Traps in Promoting Gastric Cancer Epithelial–Mesenchymal Transition Through SERPINE‐1 Expression

Gastric cancer remains a significant global health concern, with its progression and metastasis often associated with epithelial-mesenchymal transition (EMT). This study investigated the role of neutrophil extracellular traps (NETs) in promoting gastric cancer EMT by regulating SERPINE-1 expression, which encodes plasminogen activator inhibitor-1 (PAI-1). Western blot and immunohistochemistry were used to detect protein expression. Cell Counting Kit-8 was tested for cell proliferation ability using clones. The SERPINE-1 gene was knocked down using lentivirus. Immunofluorescence was used to detect the co-expression of proteins, and a Transwell assay and wound-healing assay were used to investigate the migration ability of cells. Experimental conclusions were verified in vivo using a nude mouse model. We first demonstrated overexpression of PAI-1 in gastric cancer tissues and cell lines. Subsequently, we found that NETs significantly enhanced the expression of EMT-related markers. These changes were accompanied by increases in cell invasion, migration, proliferation and tumour sphere formation. To further elucidate the mechanism, we employed lentivirus-mediated SERPINE-1 knockdown to reverse NET-induced EMT phenotype effectively. Mechanistically, we found that NETs activated the transforming growth factor (TGF)-β signalling pathway via PAI-1 as evidenced by increased expression of TGF-β1, TGF-βR1, TGF-βR2, phosphorylated Smad2/3 and Smad4. Finally, in vivo experiments using a nude mouse model of gastric cancer liver metastasis confirmed that NET-treated HGC-27 cells exhibited enhanced metastatic potential and SERPINE-1 knockdown abrogated metastatic potential. Our findings reveal a novel mechanism by which NETs promote EMT and metastasis in gastric cancer via the PAI-1-TGF-β axis. PAI-1 can be used as a potential target for the treatment of gastric cancer, and the expression of PAI-1 is closely related to the prognosis of patients with gastric cancer. Therapeutic strategies targeting NETs or PAI-1 may help prevent EMT and metastasis of gastric cancer and improve clinical outcomes in patients.