Dysplasia Subjects Research Articles

Hypomethylation of repetitive elements in blood leukocyte DNA and risk of gastric lesions in a Chinese population

BackgroundTo explore the association between hypomethylation of repetitive elements (LINE-1, Sat2, and ALU) in blood leukocyte DNA and risks of gastric lesions, and development of gastric cancer (GC), a population-based study was conducted in a high-risk area of GC in China. MaterialsMethylation levels were determined by MethyLight in 902 subjects with various gastric lesions from two cohort studies at baseline and 276 subjects with long-term follow-up data. ResultsThe frequency of LINE-1 or Sat2 hypomethylation was significantly increased in subjects with dysplasia (DYS) compared with superficial gastritis/chronic atrophic gastritis. The odds ratios (ORs) were 2.22 [95% confidence interval (CI): 1.45–3.40] for LINE-1 and 1.58 (95% CI: 1.14–2.21) for Sat2. A dose–response pattern was found for the risk of DYS and LINE-1 hypomethylation (P-trend<0.001). Further stratified analysis indicated that the frequency of LINE-1 or Sat2 hypomethylation was higher in subjects with Helicobacter pylori infection. The ORs were 1.83 (95% CI: 1.12–2.99) for LINE-1 and 1.44 (95% CI: 1.01–2.05) for Sat2. The follow-up data indicated that the risk of progression to GC was increased in intestinal metaplasia (IM) subjects with LINE-1 hypomethylation (OR=2.82; 95% CI: 1.17–6.77) or Sat2 hypomethylation (OR=2.78; 95% CI: 1.15–6.74). The risk of progression to GC was also increased in DYS subjects with Sat2 hypomethylation (OR=5.24; 95% CI: 2.00–13.74). ConclusionsThese findings suggest that hypomethylation of repetitive elements in blood leukocytes is associated with the risks of advanced gastric lesions and development of GC.

Methylation status of blood leukocyte DNA and risk of gastric cancer in a high-risk Chinese population.

To evaluate the relationship between methylation status of blood leukocyte DNA and risk of gastric cancer, a population-based study was conducted in Linqu County. Methylation levels of IGFII and N33 were determined by quantitative methylation-specific PCR. The temporal trend of methylation levels during gastric cancer development was investigated in 133 gastric cancer cases from two cohorts with pre- and/or post-gastric cancer samples. As the references of pre-GCs, 204 intestinal metaplasia (IM) or dysplasia (DYS) subjects who did not progress to gastric cancer during the follow-up period were selected. Meanwhile, 285 subjects with superficial gastritis/chronic atrophic gastritis (SG/CAG) were also selected as controls. IGFII median methylation level was significantly higher in gastric cancer cases than those with SG/CAG (61.47% vs. 49.73%; P < 0.001). IGFII and N33 methylation levels were elevated at least 5 years ahead of clinical gastric cancer diagnosis comparing with SG/CAG (63.38% vs. 49.73% for IGFII, 9.12% vs. 5.70% for N33; all P < 0.001). Furthermore, the frequency of hypermethylated IGFII was markedly increased in IM or DYS subjects who progressed to gastric cancer in contrast to those who remained with IM and DYS, and adjusted ORs were 12.52 [95% confidence interval (CI), 3.81-41.15] for IM and 10.12 (95% CI, 2.68-38.22) for DYS. Similar results were also found for N33 in subjects with IM (OR, 3.77; 95% CI, 1.20-11.86). Our findings suggested that hypermethylated IGFII and N33 in blood leukocyte DNA were associated with risk of gastric cancer in a Chinese population. IGFII and N33 methylation status may be related to gastric carcinogenesis.