The qPCR and Western blot analyses that were performed on the Eca-109, TE-1, TE-1LM, and TE-1HM cells showed that the ATF4 mRNA and protein levels increased progressively from the ESCC cells with low metastatic potential to those with high metastatic potential (Fig. S3). Here, ATF4 is linked to esophageal squamous cell carcinoma.