ABSTRACT
Background:Studies have shown that promoter methylation of MGMT gene is closely related to many malignant tumor including gastric cancer.DNA methyltransferase 1 (DNMT1) is highly expressed in many malignant tumor tissues.However, studies on relationship between methylation of MGMT gene and DNMT1 expression in gastric cancer are rare.Aims:To investigate the relationship between methylation of MGMT gene, protein expression of DNMT1 and gastric cancer.Methods:Promoter methylation status of MGMT gene in 60 gastric adenocarcinoma tissues and corresponding paracancerous tissues were detected by methylation-specific PCR (MSP).RT-PCR and immunohistochemistry were used to measure mRNA and protein expressions of MGMT and DNMT1, respectively.Results:Methylation rate of MGMT gene promoter in gastric cancer was significantly higher than that in paracancerous tissue (45.0% vs.13.3%, P<0.001).The positivity rate of MGMT mRNA in gastric cancer was significantly lower than that in paracancerous tissue (41.7% vs.93.3%, P<0.001), while the positivity rate of DNMT1 mRNA expression in gastric cancer was significantly higher than that in paracancerous tissue (76.7% vs.18.3%, P<0.001).Methylation rate of MGMT promoter in MGMT mRNA-negative expressed gastric cancer tissue was significantly higher than that in MGMT mRNA-positive expressed gastric cancer tissue (57.1% vs.28.0%, P<0.05).It showed a negative correlation between MGMT protein expression and DNMT1 protein expression in gastric cancer tissue (r=-0.795, P<0.01).Conclusions:Promoter methylation of MGMT gene and high expression of DNMT1 may be associated with the development and progression of gastric cancer.