Hypermethylation of TGF-β1 gene promoter in gastric cancer

AIM: To examine transforming growth factor-beta 1 (TGF-beta 1) promoter methylation in gastric cancer and to determine if Helicobacter pylori (H. pylori) or interleukin (IL)-1 beta could induce TGF-beta 1 hypermethylation in vitro. METHODS: We examined the frequency and extent of TGF-beta 1 promoter methylation using methylation-specific PCR in the gastric tissues from 47 gastric cancer patients and 39 non-gastric cancer subjects. H. pylori infection was confirmed by a positive result from either a serological test, histological analysis or C-13 urea breath test. GES-1 and MKN-45 cells co-cultured with H. pylori or treated with IL-1 beta for 12, 24 and 48 h in vitro tested the effects of H. pylori or IL-1 beta on TGF-beta 1. RESULTS: Twenty-four/forty-seven (51%) cases of gastric cancer (GC) tissues showed TGF-beta 1 promoter methylation, 15/47 (31.9%) cases of matched non-cancerous gastric mucosa tissues from the GC patients, and 11/39 (28%) case of the normal gastric mucosa tissues from non-GC subjects showed TGF-beta 1 promoter methylation (51% vs 28%, P < 0.05). Significantly higher levels of methylation of TGF-beta 1 were found in the tumor tissues than in non-tumor tissues from GC patients (0.24 +/- 0.06 vs 0.17 +/- 0.04, P < 0.05) and normal gastric tissues from non-GC subjects (0.24 +/- 0.06 vs 0.15 +/- 0.03, P < 0.05). TGF-beta 1 methylation was found in 48.3% of H. pylori-positive gastric mucosal tissues whereas only 23.1% of H. pylori-negative gastric mucosal tissues showed TGF-beta 1 methylation (48.3% vs 23.1%, P < 0.05). IL-1 beta appeared to induce a dose-dependent methylation of TGF-beta 1 and the strongest methylation was observed in GES-1 cells treated with 2.5 ng/mL of IL-1 beta for 48 h. Further studies showed that pre-treatment of GES-1 cells with 20 ng/mL IL-1RA for 1 h could partially abolish the effect of IL-1 beta on TGF-beta 1 methylation. Infection of GES-1 cells by H. pylori was not found to induce significant TGF-beta 1 promoter methylation. CONCLUSION: Our data revealed that TGF-beta 1 promoter is methylated in GC patients. IL-1 beta may be an important mediator for H. pylori induced gene methylation during GC development. (C) 2013 Baishideng. All rights reserved.