MMP9 and cancer: The promoter regions of the MMP9 gene in humans and mice contain binding sites for a number of oncogenic factors including the signal transducer and activator of transcription (STAT), TCF/LEF/β-catenin transcriptional complex, and NF-κB, which are all crucial in cancer cell survival and in the properties of cancer stem cells (CSC), also known as cancer-initiating cells (CIC) [8,9,10].