PPIA and esophageal squamous cell carcinoma: Inhibition of CypA decreased MMP-9 activity.53,101 CypA silencing by RNA-interfering effectively suppressed the expression of MMP-2 and MMP-9, inhibiting metastasis and invasion in gastric cancer cells.54,108 Increased levels of MMP-2 and MMP-9 have also been observed in esophageal squamous cell carcinoma and are significantly correlated with the tumor differentiation and metastasis.42 In hepatocellular carcinoma, the level of CypA expression in two HCC-derived cell lines (MHCC97-L and MHCC97-H) was shown to correlate with their metastatic capability.