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

Figure 3 O⁶-methylguanine-DNA methyltransferase is downregulated in N-nitroso compound-induced gastric epithelial cell malignant transformation. A and B: O⁶-methylguanine-DNA methyltransferase (MGMT) mRNA and protein expression in transformed gastric epithelial cells induced by N-methyl-N’-nitro-N-nitrosoguanidine (MNNG)/N-methyl-N-nitroso-urea (MNU) for 1, 4, and 8 wk; C: Cell anchorage-independent growth on soft agar for subcolones of MNNG/MNU-induced cells. C1-28: Different subcolones of MNNG/MNU-induced cells; MGMT(+): MGMT expression is upregulated in these subcolones; MGMT(-): MGMT expression is downregulated or no-changed in these subcolones; D: Apoptosis assay of MNNG/MNU-transformed subcolones after doxycycline treatment. The analyses were repeated three times, and the results are expressed as the mean ± SD. ^aP < 0.05; ^bP < 0.01. GAPDH: Glyceraldehyde-3-phosphate dehydrogenase.