Cell Lines ESCC cell lines (Eca109, KYSE150, KYSE180 and KYSE450) and human esophageal epithelial cell line HET-1A were purchased from the Shanghai Institute of Chinese Academy of Sciences Cell Collection (Shanghai, China). All these five cell lines were cultured with Roswell Park Memorial Institute-1640 medium (RPMI-1460; Gibco, Carlsbad, CA, USA) added with 10% fetal bovine serum (FBS; Gibco), 1% 100 units/mL penicillin (Gibco) and 1% 100 μg/mL streptomycin (Gibco). All cell lines were maintained at 37°C incubator with 5% CO 2. Western Blot Assay ESCC cells were collected and lysed using whole cell lysis buffer (Abcam). Protein quantification was conducted with the commercial bicinchoninic acid (BCA) protein assay kit (Invitrogen, Carlsbad, CA, USA). Proteins were separated using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) gel and transferred onto the polyvinylidene difluoride (PVDF) membrane (Millipore, Billerica, MA, USA). After blocking, the membrane was incubated with primary antibodies, including anti-XBP1 (ab37152; Abcam) and anti-glyceraldehyde-3-phosphate dehydrogenase (anti-GAPDH; ab9485; Abcam). After incubating with secondary antibody (Abcam) for 2 h, protein signals were determined using the commercial enhanced chemiluminescence kit (Amersham Pharmacia Biotech, Little Chalfont, United Kingdom).