We believe that the comparison between normal gastric epithelial cells (such as GES-1) and tumor cell lines with different histological grade, well-differentiated N87 gastric carcinoma cell line, or poorly differentiated BGC-823 cells could be included in the evaluation of NQO1 expression in gastric cancer cells, and we believe that the comparison could fully demonstrate the expression status of NQO1 in gastric cancer. Here, NQO1 is linked to gastric cancer.