SMAD2 and hepatocellular carcinoma: Further studies demonstrated that MUC1-mediated JNK activation not only enhances the phosphorylation of Smad2 C-terminal at Ser-465/467 site (Smad2C) through TGF-β/TβRI, but also directly enhances the phosphorylation of Smad2 linker region at Ser-245/250/255 site (Smad2L), and then both of them collaborate to upregulate matrix metalloproteinase (MMP)-9-mediated cell migration and invasion of HCC.