B3GAT2 and esophageal cancer: Dextrorphan O-glucuronide, which is the same alkaloid and its derivatives, is a natural human drug metabolite of dextrorphan produced by UDP-glucuronosyltransferases (UGTs) in the liver, and dextrorphan is commonly used for analgesia and belongs to the antipyretic and analgesic drugs [44], so it is not an endogenous metabolite and cannot be used as an endogenous metabolic biomarker to diagnose esophageal cancer.