MMP9 and neoplasm: Snail and Slug are a family of zinc-finger transcription factors which increase the invasiveness of tumor cells mainly by repressing the expression of the cellular tight junction protein E-cadherin and other epithelial genes such as Claudins, Occludins, and Muc1, while increasing the expression of key mesenchymal expression genes such as fibronectin (FN1) and MMP9 [28].