Post-transcriptional activation of TGF-β signaling via SMAD mRNA stabilization by EIF4A3 promotes EMT and metastasis in gastric cancer

BACKGROUND: Gastric cancer (GC) is characterized by high mortality due to late-stage diagnosis and aggressive metastatic behavior. Epithelial-mesenchymal transition (EMT), primarily driven by the TGF-β/SMAD signaling, critically contributes to GC progression. However, the molecular mechanisms regulating this pathway remain incompletely understood. METHODS: We investigated the expression, function, and regulatory mechanisms of EIF4A3 in GC using patient tissues, GC cell lines, and in vivo mouse models. We performed loss-of-function experiments and xenograft studies to assess the biological effects of EIF4A3. Mechanistic studies were applied for exploring the relation between EIF4A3 and TGF-β/SMAD signaling. RESULTS: EIF4A3 upregulation was observed in GC samples as well as cell lines compared to normal counterparts, and indicated advanced clinical stages and poor clinical outcomes. EIF4A3 knockdown markedly repressed GC cell growth and DNA synthesis in vitro, while restraining tumor growth and Ki67 expression in xenograft models. Silencing EIF4A3 impaired cell migration, invasion, and lung metastasis, and reversed TGF-β induced EMT marker expression. Mechanistically, TGF-β1 transcriptionally induced EIF4A3 via SMAD2/3 binding to its promoter. In turn, EIF4A3 enhanced TGF-β/SMAD signaling by directly binding to and stabilizing SMAD2, SMAD3, and SMAD4 mRNAs, prolonging their half-lives and promoting their phosphorylation and nuclear accumulation. Furthermore, EIF4A3 knockdown reduced SMAD2/3 phosphorylation, nuclear translocation, and downstream EMT marker expression, thereby attenuating the pro-metastatic effects of TGF-β signaling. CONCLUSIONS: Our study identifies EIF4A3 as a critical post-transcriptional regulator and downstream effector of the TGF-β/SMAD pathway. EIF4A3 forms a positive feedback loop with TGF-β/SMAD signaling, thereby reinforcing EMT and promoting metastatic progression in GC. These findings establish EIF4A3 as a novel post-transcriptional amplifier of TGF-β signaling and a promising candidate for diagnostic and therapeutic intervention in metastatic GC.