Brief Article
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World J Gastroenterol. Sep 7, 2013; 19(33): 5557-5564
Published online Sep 7, 2013. doi: 10.3748/wjg.v19.i33.5557
Hypermethylation of TGF-β1 gene promoter in gastric cancer
Yong-Qi Wang, Yu-Min Li, Xun Li, Tao Liu, Xiao-Kang Liu, Jun-Qiang Zhang, Ju-Wu Guo, Ling-Yun Guo, Liang Qiao
Yong-Qi Wang, Yu-Min Li, School of Life Sciences, Lanzhou University, Lanzhou 730000, Gansu Province, China
Yong-Qi Wang, Department of Anesthesiology, the First Hospital of Lanzhou University, Lanzhou 730000, Gansu Province, China
Yu-Min Li, Key Laboratory of Digestive System Tumors, Lanzhou 730030, Gansu Province, China
Yu-Min Li, Tao Liu, Xiao-Kang Liu, Jun-Qiang Zhang, Ju-Wu Guo, Ling-Yun Guo, General Surgery, the Second Hospital of Lanzhou University, Lanzhou 730030, Gansu Province, China
Xun Li, General Surgery, the First Hospital of Lanzhou University, Lanzhou 730000, Gansu Province, China
Liang Qiao, Storr Liver Unit at the Westmead Millennium Institute, the University of Sydney, Sydney, NSW 2145, Australia
Author contributions: Wang YQ and Li YM designed the research; Wang YQ and Guo JW performed the research; Li X performed endoscopy; Liu T performed the histological evaluation; Zhang JQ and Guo LY contributed new reagents and analytical tools; Qiao L and Liu XK analyzed the data; Wang YQ, Li YM and Qiao L wrote the paper.
Supported by The National Natural Science Foundation of China, No. 31270532; the Foundation of Key Laboratory of Digestive System Tumors of Gansu Province and the Fundamental Research Funds for the Central Universities, No. lzujbky-2011-t03-03
Correspondence to: Yu-Min Li, MD, PhD, Professor, School of Life Sciences, Lanzhou University, No. 222 Tianshui South Road, Lanzhou 730000, Gansu Province, China. liym@lzu.edu.cn
Telephone: +86-931-8942744 Fax: +86-931-8942744
Received: March 12, 2013
Revised: June 11, 2013
Accepted: July 18, 2013
Published online: September 7, 2013
Abstract

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 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 C13 urea 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-β1.

RESULTS: Twenty-four/forty-seven (51%) cases of gastric cancer (GC) tissues showed TGF-β1 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-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 20 ng/mL IL-1RA for 1 h could partially abolish the effect of IL-1β on TGF-β1 methylation. Infection of GES-1 cells by H. pylori was not found to induce significant TGF-β1 promoter methylation.

CONCLUSION: Our data revealed that TGF-β1 promoter is methylated in GC patients. IL-1β may be an important mediator for H. pylori induced gene methylation during GC development.

Keywords: Transforming growth factor-β1, Interleukin-1β, Methylation, Helicobacter pylori, Gastric cancer

Core tip:In vitro studies showed that GES-1 cells exposed to Helicobacter pylori (H. pylori) did not show significant transforming growth factor-β1 (TGF-β1) methylation. However, treatment of the GES-1 cells with interleukin (IL)-1β led to a dose-dependent methylation of TGF-β1, which was partially abolished by IL-1RA. The high levels of TGF-β1 promoter methylation in H. pylori positive patients was likely the result of H. pylori-induced inflammation rather than H. pylori itself. IL-1β may be an important mediator for H. pylori-induced gene methylation during gastric cancer development.