MMP9 and gastric cancer: In vitro tests on two gastric cancer cell lines (MKN-1 and MKN-45) and normal epithelial cells (HFE-145) using commercial ELISA kits, fluorescence resonance energy transfer (FRET) assay and Western blotting demonstrated that NT increased MMP-9 activity, cell migration, and invasion in gastric cancer cells, but not in normal cells.