U0126 can inhibit the activity of MEK/ERK by inhibiting the expression of MMP9 to reduce its invasiveness, revealing that MMP9 acts through the MEK/ERK signaling pathway, which promotes the invasion and metastasis of oral cancer cells; therefore, inhibiting this signaling pathway can reduce tumor invasion and metastasis; thus, it is considered that inhibiting the activation of this pathway is a new target in tumor therapy. This evidence concerns the gene MMP9 and neoplasm.