O6-methylguanine DNA methyltransferase is upregulated in malignant transformation of gastric epithelial cells via its gene promoter DNA hypomethylation

Figure 1 O⁶-methylguanine-DNA methyltransferase expression is enhanced in early stage gastric cancer. A: Representative images of immunohistochemistry staining for O⁶-methylguanine-DNA methyltransferase (MGMT) in early stage gastric tumor and normal tissues (n = 19); B: The mRNA level of MGMT in early stage gastric tumor and adjacent normal tissues (n = 19). The mRNA expression was normalized by glyceraldehyde-3-phosphate dehydrogenase (GAPDH); C: MGMT mRNA and protein expression in normal gastric epithelial cells and cancer cells by quantitative real-time polymerase chain reaction and immunoblot assays. GAPDH was used to normalize MGMT expression. The analyses were repeated three times, and the results are expressed as the mean ± SD. ^aP < 0.05; ^bP < 0.01. MG-C: MNNG-induced malignant transformed cell; MU-C: MNU-induced malignant transformed cell; GAPDH: Glyceraldehyde-3-phosphate dehydrogenase.