TTK and esophagitis: Several TAAs are highly expressed in EC, among which the most common TAAs have been confirmed in EC till date, including New York esophageal squamous cell carcinoma 1 (NY-ESO-1), TTK protein kinase (TTK), cancer-testis antigen 2 (CTAG2), and melanoma-associated antigen-A (MAGE-A) (42).