MMP9 and esophageal squamous cell carcinoma: miR-34a is considered as one of the most well-known miRNAs involved in the growth and progression of human tumors.32,33 Shi et al. reported downmodulation of miR-34a in ESCC cases.33 Nie et al. demonstrated that upmodulation of miR-34a culminated in increased apoptosis rate and reduced clonogenic formation, whereas it prevented invasion and migration of ESCC cells through repressing MMP-2 and -9 expressions.34 We observed that Snail-1 siRNA knockdown resulted in upmodulation of miR-34a and downregulation of MMP-9.