SMAD2 and gastric cancer: Small extracellular vesicles (sEV) derived from gastric cancer (GC) containing miR-151a-3p can be absorbed by hepatic Kupffer cells (KCs), and sEV-miR-151a-3p targets YTHDF3 and downregulates small ubiquitin-related modifiers 1 (SUMO1) translation in an m6A-dependent manner, thereby inhibiting SP3, inducing TGF-β1 expression, and promoting the formation of a local liver metastasis microenvironment through the activation of the SMAD2/3 pathway 163.