Hypermethylation of TGF-β1 gene promoter in gastric cancer

AIM:To examine transforming growth factor-β1(TGF-β1)promoter methylation in gastric cancer and to determine if Helicobacter pylori(H.pylori)or interleukin(IL)-1β could induce TGF-β1 hypermethylation in vitro.METHODS:We examined the frequency and extent of TGF-β1 promoter methylation using methylationspecific 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 C13urea breath test.GES-1 and MKN-45 cells co-cultured with H.pylori or treated with IL-1β for 12,24 and 48 h in vitro tested the effects of H.pylori or IL-1β on TGF-1β.RESULTS:Twenty-four/forty-seven(51%)cases of gastric cancer(GC)tissues showed TGF-β1 promoter methylation,15/47(31.9%)cases of matched noncancerous gastric mucosa tissues from the GC patients,and 11/39(28%)case of the normal gastric mucosa tissues from non-GC subjects showed TGF-β1 promoter methylation(51%vs 28%,P<0.05).Significantly higher levels of methylation of TGF-β1 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-β1 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-β1 methylation(48.3%vs 23.1%,P<0.05).IL-1β appeared to induce a dose-dependent methylation of TGF-β1 and the strongest methylation was observed in GES-1 cells treated with 2.5 ng/mL of IL-1β for 48 h.Further studies showed that pre-treatment of GES-1 cells with 20ng/mL IL-1RA for 1 h could partially abolish the effect of IL-1β on TGF-β1 methylation.Infection of GES-1cells by H.pylori was not found to induce significant TGF-β1 promoter methylation.CONCLUSION:Our data revealed that TGF-1 promoter is methylated in GC patients.IL-1β may be an important mediator for H.pylori induced gene methylation during GC development.