The expression of p-MEK1/2, p-ERK1/2, MMP2 (EMT-related protein) in ESCC cells was obviously downregulated by the inhibition of mitochondrial OXPHOS (Fig. 7A), indicating that CST1 might activate the MEK/ERK pathway by elevating mitochondrial OXPHOS levels in ESCC cells. This evidence concerns the gene MMP2 and esophageal squamous cell carcinoma.