CagA promotes gastric cancer stemness and metastasis via DNMT1-mediated epigenetic silencing of BEX1.

Helicobacter pylori (H. pylori) cytotoxin-associated gene A (CagA) critically contributes to gastric cancer (GC) pathogenesis, though its epigenetic control of cancer stemness is incompletely characterized. This study establishes that CagA enhances self-renewal capacity and metastatic potential in GC cells by elevating DNA methyltransferase 1 (DNMT1) expression. Upregulated DNMT1 catalyzes hypermethylation of the brain-expressed X-linked gene 1 (BEX1) promoter, resulting in transcriptional silencing of this tumor suppressor. Functional validation through tumorsphere/colony formation assays and transcriptomic profiling confirmed DNMT1-mediated BEX1 suppression as essential for sustaining stemness phenotypes. Crucially, in vivo models demonstrated that BEX1 overexpression reverses CagA-driven tumor growth and pulmonary metastasis, while BEX1 knockdown compromises the anti-tumor efficacy of DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (DAC). These findings define a novel pathogenic cascade wherein CagA initiates DNMT1-dependent epigenetic silencing of BEX1 to maintain cancer stemness. The mechanistic identification of this CagA-DNMT1-BEX1 axis provides a therapeutic rationale for targeting DNMT1 activity and restoring BEX1 function in metastatic GC. Schematic Illustration of the Molecular Mechanism by Which H. pylori CagA Protein Promotes the Maintenance of Stem Cell-Like Properties in GC Cells via DNMT1-Mediated BEX1 Methylation.