MAPK8 and gastric cancer: Further, with the MEK-dominant negative plasmid pMCL-K97M, JNK-dominant negative plasmid pMCL-TAM67 and p38 MAPK-dominant negative plasmid pMCL-mP38, we confirmed the critical roles of ERK and JNK in MMP-9 expression in gastric cancer AGS cells (Fig 3B).