Gastric cancer-derived exosomal miR-196a-5p remodels the pre-metastatic niche for peritoneal dissemination.

Peritoneal metastasis (PM) in gastric cancer (GC) remains a formidable clinical challenge. Although exosomes are critical mediators of tumor-microenvironment communication, their mechanistic role in linking mesothelial-mesenchymal transition (MMT) to peritoneal dissemination remains poorly understood. This study elucidates a GC-derived exosomal microRNA (miRNA)-driven pathway that orchestrates peritoneal metastasis. Integrated exosomal miRNA sequencing and The Cancer Genome Atlas (TCGA) analysis identified miR-196a-5p as highly enriched in GC-derived exosomes. Functional assays, including in vitro co-culture experiments, and in vivo PM models, demonstrated that GC-derived exosomal miR-196a-5p directly induces MMT in peritoneal mesothelial cells (HMrSV5) and contributed to the formation of metastatic tumors. Mechanistically, miR-196a-5p binds the 3'-untranslated region (UTR) of F-box protein 45 (FBXO45), an E3 ubiquitin ligase, suppressing its expression and thereby stabilizing snail family transcriptional repressor 1 (Snai1)-a key transcription factor in epithelial-mesenchymal transition (EMT). RNA immunoprecipitation sequencing (RIP seq), dual-luciferase reporter assays, co-immunoprecipitation (CO-IP), and rescue experiments validated the miR-196a-5p/FBXO45/Snai1 axis. Notably, miR-196a-5p disrupts FBXO45-mediated Snai1 ubiquitination and degradation, promoting MMT-driven peritoneal niche remodeling and metastatic progression. These findings reveal a novel exosome-mediated mechanism underlying GC dissemination and highlight miR-196a-5p and FBXO45 as promising therapeutic targets for PM.