MMP9 and esophageal squamous cell carcinoma: We observed by gelatin zymography or Western blotting that the treatment of ESCC cells with TNF-α significantly increased secretion of MMP9, but not of MMP2 or MMP14 (also known as membrane type 1-matrix metalloproteinase, MT1-MMP), in a dose-dependent manner (Figure 1A and Figure S1).