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

Figure 4 DNA hypomethylation contributes to O⁶-methylguanine-DNA methyltransferase upregulation in cell malignant transformation. A: Luciferase reporter assay in control and N-nitroso compound-transformed cells using PGL3-O⁶-methylguanine-DNA methyltransferase (MGMT) promoter; B and C: Methylation specific polymerase chain reaction and bisulfite genomic sequence analysis of the DNA methylation level of N-methyl-N’-nitro-N-nitrosoguanidine/N-methyl-N-nitroso-urea-induced transformed cells compared with control cells; D: Correlation of MGMT expression and DNA methylation level of MGMT promoter based on the CCLE database; E: ChIP assay with anti-DNMT1 and anti-H3K9Me3 and H3K4Me2 antibodies for analyzing the DNMT1 binding to the MGMT promoter and the H3K9Me3 and H3K4Me2 levels in the MGMT promoter. The analyses were repeated three times, and the results are expressed as the mean ± SD. ^aP < 0.05; ^bP < 0.01. M: Methylated; U: Unmethylated; IgG: Immunoglobulin G.