MMP9 and hepatocellular carcinoma: In HCC cell lines, miR-199a was found to suppress tumor proliferation and to induce apoptosis and cell cycle arrest by regulating the expression of matrix metallo-proteinase-9 (MMP-9), frizzled type 7 receptor (FZD7), and hypoxia-inducible factor-1α (HIF1α) [41,42,43].