DPYD and esophageal squamous cell carcinoma: Schneider et al. showed that the expression levels of thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), excision repair cross complementing factor 1 (ERCC1), glutathione S-transferase Pi (GST-Pi), epidermal growth factor receptor (EGFR), and HER2 genes in ESCC resection specimens dropped significantly after neoadjuvant therapy [44].