SLC52A3 and esophageal squamous cell carcinoma: C20orf54 is a human riboflavin transporter that has an important role in the intestinal absorption of riboflavin [15]–[16], and riboflavin deficiency has been associated with an increased risk of esophageal squamous cell carcinoma (ESCC) and gastric cardia adenocarcinoma (GCA).