MMP9 and neoplasm: In normal tissues, EGFR regulates the development of epithelial tissue and signal transduction, while EGFR may mutate or be overexpressed in tumor cells leading to the proliferation of tumor cells and metastasis by activating the EGFR-PI3K/AKT pathway and stimulating some matrix metalloproteinases such as MMP1 and MMP9 [63].