MMP9 and hepatocellular carcinoma: So far, it is known that KLF4 acts as a tumor suppressor by positively regulating the levels of E-cadherin in hepatocellular carcinoma [62], MMP-2 and MMP-9 metalloproteases in neuroblastoma [70] and the TF Slug during the epithelial to mesenchymal transition of mammary epithelial cells [71].