CD274 and esophageal squamous cell carcinoma: In this study, we investigated the upregulation of the programmed death ligand 1 (PD‐L1) due to epithelial‐mesenchymal transition (EMT) in ESCC using an in vitro treatment system with the EMT inducer, glycogen synthase kinase (GSK)‐3 inhibitor, and we also analyzed the correlation of EMT and PD‐L1 expression in the clinical tumor samples of both tissue microarray (TMA) samples (n = 177) and whole tissue samples (n = 21).