Loss of L1CAM from gastric epithelial cells and extracellular vesicles promotes Helicobacter pylori-driven cancer progression and invasiveness.

BACKGROUND: Helicobacter pylori (Hp) infection is a major risk factor for gastric cancer (GC). While Hp-driven alterations in host signaling have been widely studied, the contribution of extracellular vesicles (EVs) to this process remains largely unexplored. Cell adhesion molecules play key roles in maintaining epithelial integrity and their dysregulation is often associated with malignant transformation. L1 cell adhesion molecule (L1CAM), a transmembrane protein involved in cell-cell interactions and signaling, has been implicated in cancer progression but its regulation in the context of Hp infection remains unclear. Here, we aimed to determine the relevance of L1CAM regulation and its EV-associated dynamics in Hp infection-induced GC. METHODS: L1CAM status was assessed in Hp-positive gastric biopsy specimens by immunofluorescence microscopy and by western blotting of Hp-infected gastric epithelial cells (GECs). EVs from infected GECs were isolated and characterized. Functional assays, including proliferation, migration and xenograft studies were performed using infected or uninfected L1CAM-overexpressing as well as empty-vector cell-derived EVs. Integrin modulation by L1CAM was assessed by immunoblotting and microscopy in in vitro studies, patient samples and xenograft models using L1CAM-modulated cells. Epithelial-mesenchymal transition (EMT) markers, L1CAM proteolysis and inhibition studies were analyzed by immunoblotting to delineate the underlying molecular mechanisms. RESULTS: Hp infection caused a marked loss of the full-length (FL) L1CAM in GECs and secreted GEC-EVs. A similar decrease was observed in Hp-positive GC tissues and plasma-derived EVs. Mechanistically, Hp-driven loss of FL-L1CAM resulted from the metalloproteinase ADAM10-mediated cleavage and was accompanied by the appearance of L1CAM fragments in infected cells or their EVs. EVs derived from infected cells significantly enhanced proliferation and migration of non-cancerous GECs in vitro as well as promoted tumor growth in vivo. In contrast, EVs from uninfected cells attenuated these malignant traits, suggesting that Hp-associated proteolytic depletion of FL-L1CAM fosters a tumor-promoting phenotype. Additionally, loss of FL-L1CAM induced EMT and selectively decreased αVβ1 integrin across infected cells, patient biopsies and xenograft tissues, defining a distinct Hp-driven L1CAM-ADAM10-αVβ1 signaling axis. CONCLUSION: Hp-induced proteolytic cleavage of L1CAM represents a distinct molecular signature of Hp-associated GC. FL-L1CAM-depleted EV may serve as a promising minimally invasive biomarker in Hp-driven gastric carcinogenesis.