NQO1 and esophageal squamous cell carcinoma: Furthermore, the TT genotype of the NQO1 609C>T polymorphism was associated with reduced NQO1 protein expression in tumor tissues from a subset of GI cancer patients (cardiac carcinoma, gastric adenocarcinoma, esophageal adenocarcinoma, and esophageal squamous cell carcinoma) [43], [45].