Because the above experiments indicated that mesothelial cells secreted MMP-9 in response to TNF-α treatment, we designed an artificial, reconstituted mesothelium where a monolayer of mesothelial cells was cultured on a Matrigel layer in a Boyden chamber system (Figure 4A) and examined the effects of TNF-α on carcinoma cell invasion. Here, TNF is linked to carcinoma.